Electrical current measurement and rapidly locating and positively identifying cathodes having abnormal electrical conditions associated therewith in an electrolytic copper refining process tankhouse

ABSTRACT

Cathodes having abnormal electrical conditions associated therewith in an electrolytic copper refinery tankhouse are rapidly and positively identified to enable the early remedying of the abnormal condition or conditions, for instance short circuited cathodes or poor contacts, by closing the normally open, cathode bar receptive, pivotally mounted, automatically closeable and automatically openable jaws of a sensing head of an electrical current measuring instrument, or of the sensing heads of a plurality of current measuring instrument units depending from a common supporting means of a current measuring apparatus, about one or more of a plurality of spaced apart cathode bars in the tankhouse and from which the cathodes are suspended and immersed in the electrolyte. The sensing head jaws are closed about the cathode bars by lowering the instrument or apparatus whereby shoes of the instrument&#39;&#39;s operating mechanism are forcefully applied against the cathode bar or bars due to the weight of instrument or apparatus parts, thereby automatically closing the jaws of the sensing head or heads to substantially encompass the cathode bar or bars. The current passing through each cathode bar is measured by utilizing the magnetic field created by the current passing through the cathode bar to induce a measurable e.m.f. and a measurable electrical current in conductive coils on nonmagnetic cores of the sensing head jaws in a preferred embodiment. The current measurement value for the cathode bar or each of the cathode bars is compared with a predetermined desired current measurement value for its suspended cathode thereby positively identifying any cathode or cathodes having an abnormal electrical condition or conditions associated therewith.

Cited States tat Shaw [72] Inventor: Frank D. Shaw, Rumson, NJ.

[73] Assignee: American Smelting and Refining Company, New York, N.Y.

[22] Filed: Jan. 7, 1970 [21] Appl. No.: 1,108

[52] U.S. Cl. ..324/127, 324/117 R, 324/149 [51] Int. Cl ..G0lr 1/22,G01r 33/00 [58] FieldoiSearch ..324/l27, 117 R, 117 H, 149

[56] References Cited FOREIGN PATENTS OR APPLICATIONS 991,779 10/1951France ..324/l27 Primary Examiner-Rudolph V. Rolinec AssistantExaminer-Ernest F. Karlsen Attorney-Elwood J. Schaffer and Roger J. DrewI ABSTRACT Cathodes having abnormal electrical conditions associatedtherewith in an electrolytic copper refinery tankhouse are rapidly andpositively identified to enable the early remedying of the abnormalcondition or conditions, for instance short circuited cathodes or poorcontacts, by closing the normally open, cathode bar receptive, pivotallymounted, automatically closeable and automatically openable jaws of asensing head of an electrical current measuring instrument, or of thesensing heads of a plurality of current measuring instrument unitsdepending from a common supporting means of a current measuringapparatus, about one or more of a plurality of spaced apart cathode barsin the tankhouse and from which the cathodes are suspended and immersedin the electrolyte. The sensing head jaws are closed about the cathodebars by lowering the instrument or apparatus whereby shoes of theinstrument's operating mechanism are forcefully applied against thecathode bar or bars due to the weight of instrument or apparatus parts,thereby automatically closing the jaws of the sensing head or heads tosubstantially encompass the cathode bar or bars. The current passingthrough each cathode bar is measured by utilizing the magnetic fieldcreated by the current passing through the cathode bar to induce ameasurable e.m.f. and a measurable electrical current in conductivecoils on nonmagnetic cores of the sensing head jaws in a preferredembodiment. The current measurement value for the cathode bar or each ofthe cathode bars is compared with a predetermined desired currentmeasurement value for its suspended cathode thereby positivelyidentifying any cathode or cathodes having an abnormal electricalcondition or conditions associated therewith.

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sum 8 OF 9 Q INVENTOF? FRANK D 5HHW ELECTRICAL CURRENT MEASUREMENT ANDRAPIDLY LOCATING AND POSITIVELY IDENTIFYING CATHODES HAVING ABNORMALELECTRICAL CONDITIONS ASSOCIATED TI-IEREWITH IN AN ELECTROLYTIC COPPERREFINING PROCESS TANKHOUSE BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to the measurement of electricalcurrent, and more particularly to new and improved instruments andapparatus for measuring electrical current passing through one or moreconductors. Additionally this invention is directed to a method for therapid location and positive identification of cathodes having anabnonnal electrical condition or conditions associated therewith in anelectrolytic copper refinery tankhouse, thereby enabling the remedyingof the abnormal electrical condition or conditions.

2. DESCRIPTION OF THE PRIOR ART In the electrolytic copper refiningprocess, it is well understood by those of ordinary skill in the artthat a desideratum in current distribution in a tank or cell is to haveno anode to cathode short circuits, all cathodes carrying equalcurrents, and no non-current-carrying cathodes or anodes. For example,in a 10,000 ampere circuit wherein each tank has 30 cathodes, thedesired current measurement value for each cathode would be about 333amperes, obtained by dividing 10,000 by 30.

Clamp-on ammeters for measuring DC current and having normally closedtongs or jaws are known in the prior art. Such ammeters require themeter man to use two hands to open the jaws for clamping about theconductor for the current measurement, with one hand gripping the handleand the other gripping and operating a lever or second handle whichopens the jaws. Although these ammeters are understood to be useful tothe aluminum, chlorine and magnesium cell line users, due to its 7,500ampere range they are of no value or utility for measuring DC currentthrough the cathode bars in an electrolytic copper refinery tankhouse.Further, even assuming for the moment these clamp-on ammeters hadutility for cathode bar current measurement in a copper refinerytankhouse, the ammeter would be relatively slow and quite awkward forregular current efficiency work in the copper tankhouse due to requiringtwo hands for holding and opening the normally closed jaws.

Another clamp-on ammeter or current measuring instrument known in themeasuring instrument prior art has a normally closed sensing headaffixed to a handle, with the sensing head having normally closed tongsor jaws requiring a manual push-pull action on the handle by the meterman for opening for clamping about or encompassing the conductor. Aportable ammeter-containing package or unit connected to the jaws bylead wires extending through the hollow handle shows the currentmeasurement on a scale thereof by means of a pointer. The meter packagehas a handle whereby it can be carried by hand or slung over theshoulder of the meter man by a strap connected thereto. Such a clamp-onammeter was tested on cathode bars in the copper refinery tankhouse.Although such ammeter gives satisfactory results in certain respects inthe current measuring, it leaves room for improvement in the measurementof current flow through the cathode bars in the electrolytic copperrefinery tankhouse. In general this lastmentioned clamp-on" ammeterwould also be relatively slow for regular current efiiciency work in thetankhouse, which is due to the manual push-pull action required on thehandle by the meter man to open the normally closed tongs or jaws of thesensing head and then to close the jaws around the cathode bar, afterwhich the jaws have to again be manually opened by the action on thehandle to remove them from around the bar. It would be desirable in themeasurement of the cathode current in the copper refinery tankhouse tobe able to employ a current measuring instrument capable of beingclamped around each cathode bar and removed therefrom faster than suchprior art instrument having the normally closed sensing head jaws,inasmuch as a faster operating instrument from the standpoint ofencompassing and removal from each cathode bar could lead to increasedelectrical current efficiencies with higher copper cathode productionand lower costs. The aforementioned prior "tong or clamp-on" typeinstrument also may pose a problem of inconvenience and awkwardness dueto requiring both hands of the meter man for holding the instrument andexerting the push-pull action on the handle to open and close the tongsor jaws. Consequently the meter man has no free hand to hold theammeter-containing package or unit, or to move the ammeter-containingunit when slung over his shoulder to a position enabling him to take thereading from the meter panel. Further he does not have a free hand withwhich to mark cathodes having abnormal current values or to make writtenrecord of these values if such is desired. Further the jaws of suchprior clamp-on" type instrument were too large to fit easily between thecathode bars in the copper refinery tankhouse and it was only byappreciable effort and maneuvering of the jaws that the jaws were ableto clear and pass between the cathode bars to enable diagonal clampingabout the cathode bar the current through which it was desired tomeasure. This excessive size of the jaws rendered the instrumentunsuitable for regular current efficiency work in the tankhouse.

Gauss meters, which indicate the number of lines of magnetic forceadjacent to a direct current carrying conductor, are used in theelectrolytic copper refinery tankhouse, to indicate abnonnal currentconditions in a cathode bar and hence associated with the correspondingcathode. The gauss meter is located on the end of a vertical handle andmoved over the tops of the cathode bars by the meter man. The reading ofthe gauss meter is affected by distance from the cathode bar,orientation with respect to the cathode bar and by magnetic fields dueto other cathode bars and nearby supply bus bars, and hence a greatamount of skill is required of the meter man. Use of the gauss meter ingeneral does not provide a positive identification of cathodes having anabnormal electrical condition or conditions associated therewith.

Millivoltmeters have also been utilized heretofore in an electrolyticcopper refinery tankhouse for current efficiency work or troubleshooting. The millivoltmeter measures the voltage drop between eachanode and cathode. The sensing end of themillivoltmeter is usuallyinserted in the electrolyte on one side only of the cathode and betweenit and the anode. After the millivoltmeter reading is read by the meterman, the meter is jumped over the electrolyte on the other side of thatcathode and between it and the next anode and its sensing endre-immersed in the electrolyte on the other side of the anode lastmentioned and the next cathode. This pattern of immersion of themillivoltmeter sensing end is usually followed substantially the lengthof the tank. Based on the meter mans judgement of the millivoltmeterreading, he marks with chalk anodes or cathodes in association withwhich he believes an abnormal electrical condition or conditions exist,for example short circuits or poor electrical contacts, and whichrequire correction. Corrections or adjustments are then made in aneffort to eliminate the abnormal electrical condition or conditions.Later the meter man checks by millivoltmeter to determine whether theadjustments or corrections have been made and if they have, he removeshis mark. The trouble is the normal voltage drop between the anodes andcathodes depends on extraneous factors as exemplified by currentdensity, contact resistances, electrolyte composition, temperature ofthe electrolyte, amount of addition agent or agents present in theelectrolyte, anode spacing (which is continually changing as anodescorrode and after first cycle cathodes are pulled), etc. Consequentlyone must depend on the meter mans judgement and ability to determinewhat voltage is relatively high and what voltage is relatively low for agiven anode-cathode combination at that particular time, when comparedto the tank and section as a whole, The millivoltmeters, generallyspeaking, do not provide a positive identification of cathodes having anabnormal electrical condition or conditions associated therewith due tothe extraneous factors mentioned.

It is important to locate and remedy as soon as possible any abnormalelectrical condition or conditions of consequence, for instance shortcircuits, abnormally high or low cathode currents, poor contacts, etc.occurring in the tankhouse of the electrolytic copper refining process.The reason for this is that the deposition of copper at the cathode inthe electrolytic refining process is in accordance with Faradays law ofelectrolysis, and hence the amount of copper deposited at the cathode isproportional to the product of the electrical current flowing in amperesand the time the current flows.

Other tong type meters having normally closed tongs or jaws have beenemployed heretofor in electrolytic copper refinery tankhouses forcurrent efficiency work. However these meters are badly adverselyaffected by the large magnetic fields in the tankhouse, and also leaveroom for improvement from the standpoint of speeding up the currentmeasurement and efficiency work by reason of being quite slow,relatively speaking, to use and operate in that the normally closedsensing jaws must first be manually opened to encompass the conductorbar for the current measurement. Further the reliability of these metersdepends a great deal on the judgement of the meter man, and these metersdo not provide a positive identification of cathodes having an abnormalelectrical condition or conditions associated therewith.

As far as i am aware, the prior copper electrorefining art was unable tocome up with a method involving measurement of the direct currentthrough the cathode bars which would positively identify cathodes in theelectrorefinery tankhouse having an abnormal electrical condition orconditions associated therewith, and also enable such currentmeasurement and cathode identification to be carried out as rapidly asis provided by my present invention.

OBJECT OF THE lNVENTlON One object of this invention is to provide aninstrument for rapidly and accurately measuring electrical currentpassing through a plurality of spaced apart conductors or a singleconductor.

Another object of this invention is to provide an instrument for rapidlyand accurately measuring direct electrical current passing through aplurality of conductors or a single conductor, whose successful userequires only minimal operator experience,judgement, skill and effort.

Another object is to provide an instrument for rapidly and accuratelymeasuring direct electrical current passing through the cathodes in thetankhouse of an electrolytic copper refinery.

A further object is to provide an instrument for rapidly and accuratemeasuring electrical current passing through one or more conductorswhich requires only one hand of the meter man to operate, hasautomatically closeable sensing head jaws which are normally open andclose about the conductor merely by a one handed lowering of theinstrument to forcefully apply its shoes against the conductor, and hasautomatically openable sensing head jaws which open to a conductorreceptive position for the next current measurement merely by a onehanded raising of the instrument to withdraw forceful application of itsshoes from the conductor.

Still another object is to provide a method for rapidly locating andpositively identifying cathodes having an abnormal electrical conditionor conditions associated therewith in one or more tanks of anelectrolytic copper refinery tankhouse.

Another object is to provide for the more efficient and economicaloperation of the tankhouse of an electrolytic copper refinery.

A further object is to attain an appreciably increased production ofrefined copper in an electrolytic copper refinery tankhouse.

An additional object-is to provide an apparatus for rapidly andaccurately measuring the electrical current passing through a pluralityof spaced apart conductors.

Still another object is to provide an apparatus for rapidly andaccurately measuring the electrical current passing through a pluralityof spaced apart cathode bars in an elec- SUMMARY OF THE lNVENTiON inaccordance with the present invention, l have found that cathodes havingan abnormal electrical condition or conditions associated therewith, forinstance short circuited cathodes and poor electrical contacts, in anelectrolytic copper refinery tankhouse can be relatively rapidly locatedand positively identified and in this and other respects hereinafter setforth, my invention constitutes a considerable improvement over theprior art which is previously described herein. By virtue of providingfor the more rapid location and positive identification of the cathodeor cathodes having the abnormal electrical condition or conditionsassociated therewith, the present invention enables the more rapidremedying or correcting of the abnormal condition-or conditions. Themethod of the present invention, in its broader aspects, comprises, incombination, the steps of rapidly and accurately sensing and measuringthe direct electrical current passing through one or more or all of aplurality of spaced apart cathode bars each having a cathode suspendedtherefrom and immersed in electrolyte in one or more tanks in theelectrolytic copper refinery tankhouse by utilizing a magnetic fieldcreated by the current through the cathode bar or bars, and comparingthe current measurement value for each cathode bar with a predetermineddesired current measurement value for its suspended cathode therebypositively identifying a cathode or cathodes having an abnormalelectrical condition or conditions associated therewith. The directcurrent passing through any remaining cathode bars in the one or moretanks which was not sensed and measured by the sensing and measuringstep previously disclosed herein is rapidly and accurately sensedwhereby all cathode bars are current sensed and measured, and thecurrent measurement value for each of any such cathode bars is comparedwith a predetermined desired current measurement value for thecorresponding suspended cathode thereby positively identifying a cathodeor cathodes having an abnormal electrical condition associatedtherewith. The cathode or cathodes found to have the abnormal electricalcondition or conditions associated therewith are then noted in anysuitable manner, for example by marking the cathodes or cathodes withchalk; by the output device of a computer printing out the informationon paper, recording or writing the information from the computer onmagnetic tape, cards or paper tape, or producing graphic displays, theinput device of the computer having been supplied with the data; or byrecording on a chart or other suitable recording medium to obtain aprofile the current measurement values for all of the cathode bars in atank or cell or section of tank or in the entire tankhouse of theelectrolytic copper refinery. This profile of the current measurementvalues disclosed immediately above is compared with a profile of thepredetermined desired current measurement values for the cathode barsthereby identifying the cathode or cathodes having the abnormalelectrical condition or conditions associated therewith. An outputdevice of a computer which transmits signals over a teleprocessingnetwork or networks can also be employed.

Further the cathode or cathodes having the abnormal electrical conditionor conditions associated therewith can be noted by the employment of atransducer which translates pivot shaft rotation into a signal forremote readout, or by electronic scanning, with the results indicatedrecorded, printed or displayed in any suitable way.

After the cathode or cathodes having the abnormal electrical conditionor conditions have been located and identified as such, which is apositive identification of such cathodes as aforementioned, the abnormalelectrical condition or conditions are usually remedied or corrected.

The sensing and measuring of the direct current passing through thecathode bars in the copper refinery tankhouse in the method of thisinvention is preferably effected by closing the normally open, conductorreceptive sensing head jaws each including one or more electricallyconductive coils on a nonmagnetic core of a current measuringinstrument, or of a plurality of current measuring instrument units of acurrent measuring apparatus, about each cathode bar, or simultaneouslyabout all cathode bars or a plurality of such bars but less than allbars, to substantially encompass each cathode bar. In this preferredcurrent sensing and measuring, the coils of the jaws of the instrumentor of each instrument unit are electrically connected to anammeter-containing unit or package by connecting wires. By reason of thecoils of the jaws cutting the magnetic lines of force about the cathodebar or bars, the magnetic force lines being due to the current passingthrough the bars, a measurable electromotive force and hence ameasurable electrical current is induced in the coils the strength ofwhich current is measured in amperes by the ammeter of theammeter-containing unit or package. By so carrying out the sensing andmeasuring of the current, the sensing and measuring is not adverselyaffected by a neighboring magnetic field or fields resulting fromelectrical current passing through other conductors or buses.

In all embodiments of the method of this invention, the normally open,cathode bar-receptive sensing head jaws of the instrument or instrumentunits are closed or clamped, for the current measuring, about anysuitable portion of the cathode bar or bars in the copper refinerytankhouse enabling or permitting the jaws to be closed or clampedthereabout. Thus when a copper loop is used to suspend the copperstarting sheet or cathode from the cathode bar, the sensing head jaw orjaws can be closed or clamped about any portion of the cathode bar orbars on either side of the loop and between the loop edges and the sillor edge of the tank. Should another type of copper or metal suspendingmeans or device be employed for suspending the starting sheet or cathodefrom the cathode bar and which other suspending means and deviceprovides clearance for the sensing head jaws to be closed or clampedabout another portion of the cathode bar or bars than that disclosedsupra, the closing or clamping of the jaws about such other portion isentirely satisfactory.

In one embodiment of the method of the invention, the rapid and accuratesensing and measuring the current is carried out with respect but one ofthe plurality of spaced apart cathode bars each having the cathodesuspended therefrom and immersed in the electrolyte in the copperrefinery tankhouse, and the current measurement value for the cathodebar is compared with a predetermined desired current measurement value,usually an optimum current measurement value, for its suspended cathodethereby positively identifying the cathode as having an abnormalelectrical condition or conditions associated therewith when suchabnormal condition or conditions exists. The steps of sensing andmeasuring and then comparing the current measurement value of thecathode bar with the predetermined desired measurement value are thenrepeated in that sequence on all remaining cathode bars in the tank oneat a time. The remainder of the method of this em bodiment substantiallyis the same as is previously disclosed herein for the method in itsbroader aspects.

In another embodiment of the method herein, the rapid and accuratesensing and measuring of the current is carried out simultaneously withrespect a plurality of the spaced apart cathode bars and which may beall or less than all but still a plurality of the cathode bars in atank, section, or even the tankhouse, and the current measurement valuefor each cathode bar is compared with a predetermined desired currentmeasurement value, usually an optimum current measurement value, for itssuspended cathode thereby positively identifying the cathode as havingan abnormal electrical condition or conditions associated therewith whensuch abnormal condition or conditions exists. In the event less than allof the cathode bars in the tank, section, or tankhouse, as desired, hadthe current passing therethrough sensed and measured, the rapid andaccurate sensing and measuring is conducted with respect the remainingcathode bar or bars and the current measurement value for each such baror bars compared with a predetermined desired current measurement value,usually the optimum current measurement value, for its suspended cathodethereby making the positive identification referred to immediatelyabove. The remainder of the method of this embodiment is substantiallythe same as previously disclosed herein for the method in its broaderaspects.

In certain embodiments of the apparatus of this invention, the currentmeasuring instrument has normally open, conductor receptive, pivotallymounted, automatically closeable and automatically openable sensing headtongs or jaws. The current measuring instrument is a portable instrumentand is easily lowered by the meter man with only one hand (leaving theother hand free) to apply the instruments shoes to the cathode bar oranother solid surface in the tankhouse and to position the tongs or jawsabout the cathode bar. Due solely to the weight of instrument partsincluding the sensing head jaws and a yoke assembly, the jaws closeabout the cathode bar with the lowering of the instrument tosubstantially encompass the bar for the current measuring. Upon raisingor lifting of the instrument by the meter man, again easily done withbut one hand, from the cathode bar with attendant withdrawal of forcefulapplication of and ultimately of contact of the shoes from the cathodebar or other solid surface, the jaws open to their conductor receptiveposition ready for the next measurement again due solely to the weightof instrument parts including the sensing head jaws and a yoke assembly.The meter man merely walks rapidly, compared with the prior artmetering, down the length of the tank or cell usually on the cathodebars to repeat this procedure of lowering the instrument toautomatically close the jaws about each cathode bar and, after takingthe current measurement reading on the ammeter-containing unit orpackage, raising or lifting the instrument to automatically open thejaws to receive the next cathode bar.

In anotherembodiment of the apparatus herein, a plurality of currentmeasuring instrument units depends or is supported from a commonsupporting means. The measuring instrument units each have normallyopen, conductor receptive, pivotally mounted, automatically closeableand automatically openable sensing head jaws, and the instrument unitsare lowered and raised to and from the cathode bars in the tankhouse bya crane, or any other suitable raising and lowering device, for instancea suitable raising and lowering device or means mounted on an integralcarriage or bridge on wheels spanning and straddling the entire tank orcell. The jaws of the instrument units close about the cathodes for thecurrent measuring upon lowering the apparatus, to bring the instrumentunit shoes in forceful contact with the cathode bars or other solidsurfaces, and open upon raising or lifting of the apparatus to withdrawthe forceful application of and ultimately the shoes from the cathodebars or other solid surfaces, solely by reason of the weight ofapparatus parts including the sensing head jaws.

Alternatively, the jaws of the electrical current measuring instrumentor instrument units of the current measuring ap paratus may bemaintained in the normally open, conductor receptive, ready position forpositioning about the cathode bar or bars by the biasing or urgingaction of a helical spring or springs, or by the combination of theweight of instrument parts including the jaws and the urging action ofthe spring or springs, instead of by only the weight or mass ofinstrument parts.

The current passing through each cathode bar in the tankhouse of theelectrolytic copper refinery is measured either directly or indirectlyin accordance with the present invention. The sensing head or heads ofthe current measuring instrument or instrument units herein utilizeseither directly or indirectly the magnetic field created by the currentpassing through the conductor or conductors to obtain the value of thecurrent passing through the cathode bars in the copper refinery andhence the cathode current values. The cathode bar or cathode currentvalues directly or indirectly obtained are suitable for a plurality ofdifferent readouts, including direct and indirect readouts such as forinstance a pivoted or swin gable indicating needle on an ammeter scale,a transducer which translates pivot shaft rotation into a signal forremote readouts, or electronic scanning, with the result or resultsindicated, recorded, printed or displayed in any useful way. Further, aspreviously disclosed herein, a computer can be employed in conjunctionwith the current measuring instrument herein and especially inconjunction or association with the current measuring apparatus hereinhaving the plurality of current measuring instrument units, the outputdevice of the computer printing out or otherwise recording or writingthe information as previously disclosed herein or graphically displayingcathode current values and/or identifying cathodes whose current areabove or below predetermined desired or optimum current values or arefluctuating as may be the case where an unstable short circuit orvarying resistance contact exists.

The sensing head of the current measuring instrument of this inventionpreferably utilizes for current measuring purposes the magnetic fieldcreated by the current passing through the conductor either inducing ameasurable electromotive force and a measurable electrical current inthe coil or coils of the sensing head's nonmagnetic jaws by reason ofthe coil or coils of the jaws cutting the magnetic lines of force duringmovement of the jaws about the conductor in accordance with Flemingsright hand rule, or, in another embodiment concentrating or inducing themagnetic field in the non-retentive magnetic jaws of the sensing headwherein a movable permanent magnet needle, or a Hall effect element ortransducer is utilized to respond to the magnetic field created by thecurrent in the conductor in such manner as to determine the value of thecurrent passing through the conductor. ln the electrolytic copperrefinery tankhouse, the induction of a measurable e.m.f. and ameasurable current in coils of sensing head nonmagnetic jaws with thecoils about nonmagnetic cores is preferred as previously mentioned, byreason of not being adversely affected by neighboring magnetic fields inthe refinery tankhouse.

A desired current measurement value, which is usually but notnecessarily an optimum current measurement value, is determined orcalculated for each cathode, and the current measurement value for eachcathode bar and hence cathode is compared with this predetermineddesired or given current measurement value whereby an abnormalelectrical condition or conditions, if occurring, is positively locatedand its remedying or correcting enabled. In the electrolytic copperrefining process, there is usually a plus and minus deviation from apredetermined optimum current measurement value within which one cansatisfactorily electro-refine copper, the deviation being decided uponin accordance with practical mechanical, labor, and electrochemicalfactors applying to the particular electrolytic copper refinery, oneparticular factor being the cathode age or length of time it has been inthe tank, For example due to its light weight and tendency in the firstseveral days of its growth to warp, and due to stress relieving by thehot electrolyte, plus and minus deviations from optimum current whichone can practically correct would generally be higher than in later daysof cathode growth. The predetermined optimum current measurement valuefor the cathode and hence the cathode bar, is determined from optimumcurrent density and total current carrying surface area of the cathode.Thus if optimum current density is 20 amperes per square foot, then theoptimum current for a cathode with a total current carrying surface areaof 16.7 square feet is 16.7 multiplied by 20 or 334 amperes. Undesirableresults of operation above optimum current density include cessation ofcurrent flow due to anode polarization, dendritic short circuitingcopper growths from cathode to anode, and increase in impurity levels incathode copper. The principal undesirable result of operation belowoptimum current density is below capacity production. Operation withboth above and below optimum current density results in unequal anodeerosion which further contributes to unequal current density byproducing unequal anode to cathode spacing and possible anode structuralcollapse. Allowance would be made for the practical factors heretoforementioned affecting current balance among cathodes in a tank or cell,such allowance being, for example, plus or minus 20 percent of optimumcurrent.

The sensing head jaws can be of any suitable shape or configuration, forexample arcuate, hemielliptical so as to form an ellipse when closedabout the conductor, right angular so as to form a square when closedabout the conductor, or generally of any such shapes or configurations.in the measuring of the cathode current in a copper refinery tanlthouse,the sensing head jaws of the instrument or instrument units are of suchdimensions that the jaws have clearance to pass, when in the open,conductor receptive position, between the cathode bar the current ofwhich is to be measured and two cathode bars laterally spaced at theopposite sides of the first-mentioned cathode bar. Thus the overallwidth of the sensing jaws, i.e. the distance from the lateral outermostedge portion of one of the jaws to the lateral outermost edge portion ofthe other jaw, when open is such that the jaws have clearance to passbetween the cathode bar the current of which is to be measured and thetwo cathode bars laterally spaced at the opposite sides of thefirst-mentioned bar. In closing or clamping about the conductor toeffect the measurement of the current passing therethrough, the sensinghead jaws may or may not contact the conductor.

The present invention constitutes a considerably improvement in this artby reasons of: (l) rapidly locating and positively identifying cathodeshaving an abnormal electrical condition or conditions associatedtherewith, for instance short circuited cathodes or poor contacts, inone or more tanks or cells of the electrolytic copper refinerytankhouse; (2) enabling the remedying of the abnormal electricalcondition or conditions associated with the cathodes 'to be made soonerthan by the prior art techniques by reason of( 1) supra; (3) attaining aconsiderably increased production of refined copper in the electrolyticcopper refining process; (4) enabling an appreciably more efficient andeconomical operation of the tankhouse of the electrolytic copperrefinery; (5) the instruments rapidly and accurately measuringelectrical current passing through a plurality of conductors, or asingle conductor, requiring but one hand to operate, requiring onlyminimal experience, judgement and skill of the meter man for itssuccessful use; (6) the instruments having automatically closeabio andautomatically openable sensing head jaws and enabling the meter man torelatively rapidly move down the line of cathode bars in theelectrolytic copper refinery tankhouse to measuring the direct currentpassing through each bar; (7) the instruments and apparatus in apreferred form, being virtually unaffected by the magnetic field ofother current carrying conductors such as, for instance, adjacentcathode bars and/or high current buses; and (8) the apparatus having theplurality of current measuring instrument units ef fecting thesimultaneous measurement of current through all cathode bars in a tankor cell, in a section, or in the entire tankhouse of the electrolyticcopper refinery, or in a plurality but less than all cathode bars insuch loci, as desired.

in those embodiments of the invention utilizing a single currentmeasuring instrument of the invention, the present invention enables theoperator or meter man with a singlehanded alternately lowering andraising motion and movement of the portable measuring instrument herein,to relatively rapidly move down the line or row of spaced apart cathodebars in the electrolytic copper refinery tankhouse by walking on thecathode bars to measure the direct current passing through the cathodebars and to rapidly locate any cathodes having associated therewith anabnormal electrical condition or conditions, e.g. short circuitedcathodes or poor electrical contacts; and to identify such cathodespositively, i.e. admitting of little or no question in identifying thecathode or cathodes as having the abnormal electrical condition orconditions associated therewith.

The current measuring instrument or apparatus of this invention has arange of from to 1,000 amperes in the embodiments having the one or moreconductive coils in each jaw of the sensing head, and the model ASARCOCOP ammetercontaining package or unit connected to the sensing jawcoils. This range renders the instrument or apparatus well suited forthe important use of measuring the cathode current in the tankhouse ofan electrolytic copper refinery. The current measuring instruments orapparatus of this invention having the non-retentive or soft" magneticjaws may also have a range of 0 to 1,000 amperes.

The current measuring instruments and apparatus of this invention isalso utilizable for measuring the electrical current passing through anyother electrical conductor or conductors, in addition to that throughthe cathode bars in the electrolytic copper refinery tankhouse, and forany purpose or reason. When the current measuring instrument isutilized, the conductor or conductors may be at any location relative tothe meter man, for instance below, above or laterally at the side orsides of the meter man. When the current measuring apparatus having theplurality of current measuring instrument units is utilized, it isimperative that the current carrying conductor or conductors be in alocation which requires lowering of the apparatus and its instrumentunits so that the sensing head jaws of the instrument unitssubstantially encompass the corresponding conductors. The currentmeasuring instruments and apparatus herein has utility in anyelectrolytic process wherein it is desirable to locate and correct anyabnormal electrical condition or conditions, or for any other purpose orreason. Of course the equipment or apparatus utilized in theelectrolytic process must be of such structure or construction as toenable the use of the measuring instrument or apparatus herein.Exemplary of known electrolytic processes in which the instrument ofthis invention is utilizable for electrical current measurement are theprocesses for the electrolytic production of aluminum (the HalH-Ieroultprocess being but exemplary), electrolytic production of magnesium,electrolytic production of nickel, electrolytic production of manganese,and production of chlorine by the electrolysis of brine, electroplatingprocesses, e.g. the electroplating of zinc, electroplating of nickel,electroplating of silver, electroplating of gold, electroplating ofcopper, electroplating of cobalt, and the electroplating of alloysthereof, e.g. cobalt-nickel alloys, brass, nickel-copper alloys andnickel-zinc alloys. In the aforementioned electrolytic processes ineffecting the electrical current measurement, the sensing head jaws ofthe measuring instrument of the invention is preferably closed orclamped about an electrical conductor bar or bus bar or other shapeconductor connected to and removing electrical current from the cathode.However in the process for the electrolytic production of aluminum, itmay be more desirable due to the structure and shape of the processequipment to close or clamp the sensing head jaws about a bus bar orbar-shaped conductor or other shape conductor connected to and supplyingelectrical current to the anode.

Larger and smaller ranges can be utilized in the current measuringinstruments or apparatus of this invention than the 0 to 1,000 ampererange hereinbefore disclosed, and may be indicated for use of theinstrument or apparatus for other processes than the electrolytic copperrefining process. For

example, for use of the instrument having the coils in the sensing headjaws for the measurement of direct current in the electrolytic processesfor the production of aluminum, chlorine or magnesium, a larger rangefor the measuring instrument of up to 10,000 amperes and higher may berequired. This higher range of up to 10,000 amperes and higher isprovided by increasing the size of the electrical and mechanicalcomponents of the instruments, and by modifying the sensing head andcurrent measuring and any other components as may be required.

Where the process voltage levels so dictate, safety considerations mayrequire that electricians gloves be worn by the meter man or operator innormal operation of the instrument.

In the electrolytic refining of copper the impure copper to be refinedis cast in plate form as anodes. The anodes are suspended inelectrolytic tanks in the tankhouse in alternation with copper startingsheets suspended from the cathode bars as cathodes and immersed in anelectrolyte, usually an aqueous acid solution containing copper sulfateand sulfuric acid. When a direct electrical current is passed throughthe electrolyte from the anodes to cathodes, the copper is dissolvedfrom the anodes and deposits on the cathode starting sheets. Theimpurities associated with the impure copper of the anodes collects atthe bottom of the electrolizing tanks in the form of anode mud or slime.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS Reference is made to theaccompanying drawings wherein:

FIG. 1 is a perspective view of a current measuring instrument of theinvention.

FIG. 2 is a vertical sectional view taken on line 22 of FIG. 1.

FIG. 3 is a schematic view of the current measuring instrument of FIG. 1with its sensing head jaws in an open, conductor-receptive positionpositioned about a cathode bar in the tankhouse of an electrolyticcopper refinery.

FIG. 4 is a schematic view of the current measuring instrument of FIG. 1with the sensing head jaws in an intermediate partially closed positionabout the cathode bar.

FIG. 5 is a schematic view of the current measuring instrument of FIG. 1with the sensing head jaws in a final, closed position about the cathodebar.

FIG. 6 is an end elevational view of the lower end portion of thecurrent measuring instrument of FIG. 1.

FIG. 7 is a plan view partly broken away of the hinge means of thecurrent measuring instrument of FIG. 1.

FIG. 8 is an end elevation partly in section of one of the connectinglinks of the instrument of FIG. 1.

FIG. 9 is a horizontal sectional view taken on line 9-9 of FIG. 6.

FIG. I0 is a vertical sectional view taken on line 10-10 of FIG. 11.

FIG. 11 is a side elevational view of the yoke assembly of the currentmeasuring instrument of FIG. 1 and also showing a crossbar and a shoe ofthe instrument.

FIG. 12 is a horizontal section through an end portion of one jaw memberof the measuring instrument of FIG. 1.

FIG. 13 is a side elevational view of a current measuring instrument inaccordance with another embodiment of the invention.

FIG. 14 is a vertical sectional view taken on line 14-44 of FIG. 13.

FIG. 15 is a horizontal sectional view taken on line 15-15 of FIG. 16.

FIG. 16 is an end elevational view of a portion of the support memberand hinge member of the current measuring instrument of FIG. l3.

FIG. 17 is a vertical sectional view taken on line l717 of FIG. 14.

ill

FIG. 18 is a view of the sensing head portion including a currentreadout device of a current measuring instrument in accordance withstill another embodiment of the invention, the sensing head beingdisconnected from the remainder of the instrument and having its jawsclamped about a cathode bar in the tankhouse of an electrolytic copperrefinery.

FIG. 19 is a side elevational view of a current measuring apparatus ofyet another embodiment of this invention prior to clamping the apparatusjaws about a plurality of spaced apart cathode bars in the tankhouse ofan electrolytic copper refinery, the apparatus comprising a plurality ofcurrent measuring instrument units.

FIG. 20 is a side elevational view of the current measuring apparatus ofFIG. 19 after clamping or closing of the apparatus jaws about the spacedapart cathode bars.

DETAILED DESCRIPTION Referring to FIG. 1, the current measuringinstrument comprises elongate supporting tube or handle 15, a yokeassembly 31 including inverted generally U-shaped yoke member 32 movableon the handle, and tong-like sensing head 55 including normally open,conductor receptive, hinged, automatically closeable and automaticallyopenable, tong-like jaws 56 when the instrument is held in a generallyvertical orientation with the jaws 56 suspended below the supportingtube. Jaws 56 have electrically conductive coils composed of amultiplicity of windings wound on a non-magnetic or non-magnetizablecore, shown in FIGS. 2 and 9 and hereinafter described, andammeter-containing package 77 is electrically connected to theconductive coils of sensing jaws 56 by suitable conductors. Referringnow to FIGS. 1-6 of the drawings, elongate supporting tube or handle 15comprises upper tubular section 16 of stainless steel attached to lowertubular section 17 of stainless steel by a flexible joint includinginner, concentric, smaller diameter, relatively thin wall tube 18 ofstainless steel, shown in FIG. 2, intermediate tubes 19 shown in FIG. 2of compressible flexible material, for instance Tygon, coaxially alignedbetween smaller diameter tube 18 and upper handle section 16 and betweensmaller diameter tube 18 and lower handle section 17, and stainlesssteel screws 20 with stainless steel double locking nuts insertedthrough registering apertures in upper section 16, inner tube 18 andtube 19 and in lower section 17, inner tube 18 and tube 19. The flexiblejoint by which upper handle section 16 is attached to lower handlesection 17 functions to prevent the application of damaging force to themechanism parts or the sensing head hereinafter described appliedthrough supporting tube or handle 15. A handle or handgripping assembly21 comprises stainless steel collar 22 having a sliding fit over upperhandle section 16, collar 22 being drilled and tapped to provide twointernally threaded apertures or holes each approximately 180 from theother. Two adjustable handle arms 23 of stainless steel each knurled atits outer end portion and threaded at its inner end portion, extendradial to collar 22 and are screwed within the correspondinglyinternally threaded apertures of collar 22 to lock this handle assemblyto upper handle section 16 at any desired location by a jam fit.Compressible discs 24 of a flexible material, for instance Neoprene,"are disposed between the inner ends of arms 23 and the upper handlesection 16 to avoid slippage of the handle assembly on the upper handlesection. Tubing 25 of Neoprene" is disposed over arms 23. Crossbar 27 ofstainless steel is affixed by a jam fit or by welding or otherwise in aslot in a lower portion of lower tubular section 17 of supporting tubeor handle 15, pivot pins 28 being inserted through apertures in itsopposite end portions and through transverse, axially alignedregistering apertures 62 in the slotted end portions of linkage arms 54,shown in FIG. 8, which receive the crossbar end portions in their slots.Lower section 17 of the supporting tube or handle has a generallyinverted T-shape due to its crossbar 27 when the instrument is in agenerally vertical orientation with the jaws below the handle.

Yoke assembly 31 comprises inverted generally U-shaped yoke member 32 ofstainless steel, shown in FIGS. 1, 6 and W, welded to yoke sleeve 30also of stainless steel, which is movable or slideable on the lowersection 17 of supporting tube ll5. Movable yoke sleeve 30 has slot 29,shown in FIG. 10, in its lower portion with slot 29 being of slightlylarger width than the thickness of crossbar 27. Bushing 33 of "Teflon"or another low friction coefficient material is press fitted over theinner surface of sleeve 30 and between handle section 17 and sleeve 30,to permit free movement of the yoke assembly on the lower handle section17 of the supporting tube. Set screw 40, shown in FIG. 10, threadablyremovably inserted in a correspondingly threaded opening through sleeve30 and bushing 33 serves to aid in holding bushing 33 in place. Bushings34a of Teflon" are provided in aligned apertures 34 in yoke member 32for hinge pin or shaft 35. Two spaced apart, elon gate crossbars 36,shown in FIGS. ll, 2 and 11, are attached to a lower portion of the legsof the inverted generally U-shaped yoke member 32 by stainless steelscrews 37. Crossbars 36, which were of stainless steel and substantiallyparallel as shown, each extend an appreciable distance laterally beyondthe side edges of each leg of yoke member 32, with the lowermost edge ofeach crossbar, when the instrument is held downwardly with the sensinghead below the supporting tube, being above a lower edge of each shoehereinafter disclosed. The crossbars 36 function to render the apparatusfree-standing when the tong-like jaws of the sensing head hereafterdescribed are closed around a conductor such as, for instance, cathodebar 39 in a copper refinery tankhouse, gravity causing the apparatus tobe supported on the two legs of the inverted generally U-shaped yokemember 32 and on one or more of the crossbars 36, to protect the sensinghead and mechanism, and to serve with the top of the supporting tube orhandle as a three point stable support for the mechanism when laid on ahorizontal surface. The length of crossbars 36 can be reduced, ifrequired, to fit between adjacent conductor bars such as the cathodebars 39. Crossbars 36 have apertures 41 for purpose of weight reduction.Inverted generally U-shaped yoke member 32 as shown also has apertures42 in its legs for weight reduction.

Shoes 43 of an electrically insulating or substantially nonelectricallyconductive material such as, for instance, Teflon, are attached to thelower or end portions of the legs of yoke member 32 by screws 44 andextend a short distance beyond the ends of the yoke member legs. Shoes43 are replaceable by removal of the screws. The electrically insulatingmaterial of shoes 43 insulate the mechanism from electrical contact withthe electrical current carrying conductor bar 39, when shoes 43 are incontact with the conductor bar 33. Shoes 43 may also be of a moreresilient electrically insulating material such as Neoprene to reduceimpact.

Hinge 45, shown also in FIG. 7, comprises hinge plates 46 of stainlesssteel each affixed at their inner end upper edge portions by welding toone of annular members or sleeves 49 of stainless steel. Thus, one ofthe annular members or sleeves 49 is affixed by welding to an inner endupper edge portion of one of the hinge plates 46 and the other annularmember or sleeve 49 is affixed by welding to the inner end upper edgeportion of the other hinge plate 46. Pivot pin or shaft 35, which issubstantially centrally located with reference to the hinge plates 46,extends through bushings 34a fitted in orifices 34 in generally U-shapedyoke member 32 as well as through bushings 40a fitted in the passagewaysof axially aligned tubular members or sleeves 49, such orifices 34 inyoke member 32 registering with the passageway of sleeves 49. Snap rings47 of Teflon, shown in FIG. 6, serve to hold pivot pin 35 in place, andTeflon washers designated at 48 in FIG. 6.

Annular members 50 of stainless steel are welded to angular, downwardlybent outer end portions or ears 51 of binge plates 46. Bushings 52 inthe apertures of annular members 50 accommodate the pivot pins 53 forthe links 54. The generally arcuate tong-like jaws 56 of the sensinghead 55 are secured to hinge plates 46 by screws 57 inserted throughholes 58, shown in FIG. 7 and drilled through hinge plates 46, and intotapped holes or cavities in the upper portion of the tong-like jaws 56and registering with the holes 58 in hinge plates 46. Jaws 56 eachinclude a non-magnetic core having a conductive coil or coils on eachcore encapsulated in or coated with a substantially continuous layer ofa resin which is substantially noncorroding in acid conditions when theinstrument is utilized for current measurement in the electrolyticcopper refinery tankhouse, or is substantially non-corroding in alkalineconditions or in acid and alkaline conditions when the instrument isemployed under those conditions. A suitable material for such layer isan epoxy resin inasmuch as it is substantially non-corroding in bothacid and alkaline conditions.

Links 54 are pivotally connected to and link outer end portions ofcrossbar 27 by pivot pins or shafts 28 inserted through the registeringapertures 62 in each link 54 and in crossbar 27 with the outer endportions 51 of the hinge plates 46 and to which hinge plate outer endportions links 54 are also pivotally connected, by pivot pins or shafts53 inserted through the registering apertures 63 in the other endportions of links 54 and the passageway or apertures through axiallyaligned annular members 50. Each link arm 54 has a longitudinallyslotted or bifurcated end portion 59, shown in FIG. 8, for insertion ofcrossbar 27 in the slot, with the opposite non-slotted, apertured endportion of each link 54 positioned between-the annular members 50.Bushings 60 and 61 of Teflon are pressed into apertures 62 and 63 atopposite ends of each link 54. Bushings60 at the slotted ends of links54 were pressed into aperture 62 prior to cutting slot 59 in each arm54. Shiftable collar 65 of stainless steel, which functions to limit theextent of opening of the tong-like jaws 56 and which has a sliding fiton sleeve 30, is secured in the desired location on sleeve 30 by lockingscrew 66. Cushion washer 67 of Neoprene or of any other suitableresilient material is cemented to collar 65 and serves as a cushion orbumper between crossbar 27 upon the opening of jaw members 55 and collar65. If desired, plates 68 of stainless steel or of other suitableprotective material can be secured to links 54 by screws and serve tocover the openings between the legs of yoke member 32 and links 54 toprotect the wires 78. Plates 68, present in the instrument of FIG. 2,are detached from the instrument of FIGS. 1 and 3-6 for purpose ofclarity in showing detail.

Shiftable collar 69 of stainless steel is disposed on lower handlesection 17, collar 69 being locked at a desired or predeterminedlocation on lower handle section 17 by locking screw 72. The closing ofjaws 56 around cathode bar 39 results in upward travel of sleeve 30 onlower handle section 17, and the predetermined position of collar 69locked on lower handle section 17 is such that compressible bumperwasher 70 of Neoprene" atop sleeve 30 cushions and stops the upwardmovement of sleeve 30 and hence cushions the closing of jaws 55.

When the instrument is to be used to measure current passing through aconductor located overhead or laterally of the meter man, helical spring73, shown in FIG. 6, is employed and is disposed in compression aboutthe exterior of lower handle section 17, between collar 69 and yokesleeve 30, spring 73 hearing against an end portion of movable yokesleeve 30 and against end 71 of collar 69. Compressible bumper washer70, shown in FIG. 2, is ordinarily not utilized when spring 73 isemployed. Collar 69 is locked at a desired or predetermined location onlower handle section 17 to provide the desired degree of compression inspring 73 and hence the desired degree of biasing of or forceapplication against movable yoke sleeve 30 to move in a direction awayfrom the collar end 71, such biasing of yoke sleeve 30 being sufficientto effect the automatic opening of jaws 56 and the maintaining of thejaws in an open position when shoes 43 are not forcefully appliedagainst a conductor, Consequently the tong-like jaws 56, which arepivotally mounted on the inverted generally U- shaped yoke member 32welded to the yoke sleeve 30, are opened and maintained in theirnormally open position (except when shoes 43 are forcefully appliedagainst the conductor) in positions of the instrument wherein thesensing head jaws are located above the handle or supporting tube or atthe end portion of the supporting tube when held laterally of the meterman as well as in positions of the instrument wherein the sensing headjaws are suspended below the handle or supporting tube, for instance, inthe use of the instrument to close its jaws around the electricalconductor located overhead, or located laterally beside the meter man oroperator as well as when located below the normal level of the metermans hands when standing with his arms depending limply at his sides, tomeasure the electrical current passing therethrough. Further, coilspring 73 serves to cushion the closing impact of the jaws 56 due toincreasing compression of spring 73 as the jaw faces meet. When theinstrument is to be used only for measuring current through a conductorlocated below the normal level of the meter man 5 hands when standingwith arms held limply at his sides, for a light compression or nocompression position for spring 73, if desired, collar 69 is moved fromits solid line heavy compression position, shown in FIG. 6, to thedotted line position where it is locked on lower handle section 17 bylocking screw 72.

Jaws 56 of sensing head 55 have electrically conductive coils 75, shownin FIGS. 2 and 9, each composed of a multiplicity of wire windings orturns wound on a non-magnetic core 76. The wire windings of coils 75 areof copper or another metal or material of good electrical conductivity,with the wire being coated with a thin layer of electrically insulatingmaterial, for example an electrically insulating enamel layer. The core76 is of aluminum or any other suitable nonmagnetic or non-magnetizablematerial. Coils 75 on cores 76- are covered with or encapsulated in anelectrically-insulating, corrosion resistant, mechanical attack andabrasion-protecting, non-magnetic substantially continuous layer 81 of amaterial possessing such properties in the layer, for instance asynthetic resin, e.g. an epoxy resin, having such properties or of anyother suitable material having such properties in the layer. Layer 81can be a thin or thick layer and typically is of thickness in the rangefrom one-sixteenth inch to one-fourth inch. Each coil 75 can have one,two, three or more layers of windings or turns, and there can be asingle coil in each jaw 56 or two or more coils connected in series.Coils 75 are adapted to be operatively connected with the direct currentmeasuring meter package or unit 77 including an ammeter and, as shown inFIG. I, are electrically connected to such meter package or unit byconductor wires 78 extending through suitable apertures (not shown) intong-like jaws 56, through apertures 79a, shown in FIG. 7, in hingeplates 46 and through the hollow handle sections 17 and 16 and thehollow flexible joint therebetween, wires 78 emerging through anaperture 78a or apertures in upper handle section 16 as a flexible lead,coiled or uncoiled, and being electrically connected to meter unit 77 byplug 79, shown in FIG. 1. Wires 78 are provided with malefemale spliceconnectors 78c in the vicinity of the flexible joint section to permitassembly and disassembly of the upper and lower handle sections 16 and17 respectively and to permit replacement of the wires 78. An envelope78b of substantially non-electrically conductive sealant material, forinstance silicone sealer, is preferably employed to surround anotherwise exposed portion of the wires 78 after they emerge from jaws 56and hinge plates 46 and before they enter the lower end of thesupporting tube lower section 17, for protective and supportingpurposes. The ends of coiled flexible sections 78d of wires 78 are alsoencased in envelopes 78e of the substantially non-electricallyconductive sealant material, which restricts flexing of wires 78 totheir coiled flexible sections 78d. This avoids wire breakage due tofatigue failures which otherwise may result if bending due to openingand closing of jaws 56 is allowed to concentrate at single points inwires 78. An end plate 88, shown in FIG. 12, is secured by screws to theconfronting end face of each jaws 56 to prevent wear due to attrition bycontacts with cathode bar 39. End plates 88 can be fabricated of anysuitable non-magnetic material, for instance non-magnetic stainlesssteel.

Meter package or unit 77, which includes an ammeter, is shown in FIG. 1and obtained from Halmar Electronics, Inc., 1544 West Mound St.,Columbus, Ohio as Model ASARCO COP. Meter package 77 is battery poweredand ready to give a current measurement reading at all times on itsscale by means of a pointer which moves over the scale. Meter package 77contains an ammeter 76, electronic circuit components, switches andbattery in the single package. Meter unit 77 has a casing preferablywith a relatively short length of tube 80 secured to the back side platethereof, tube 80 being of slightly larger diameter than the diameter ofthe tubular upper handle section 16 whereby meter 77 rests on upperhandle section 16 as shown. A plug of an elastomer or other suitableflexible material may be inserted in the top of hollow upper handlesection 16 for cushioning meter unit 77. Mounting of the meter unit 77by means of tube 30 and the flexible lead wires 73 emerging from theupper handle section 16 permit removal of the meter unit for operationof the instrument with the meter unit 77 hand held, if desired.Alternatively, the ammeter, switches, battery and electronic circuitcomponents of meter unit 77 may be mounted separately or in variouscombinations at locations other than the top of upper handle section lieto suit individual preferance. For example, the ammeter 76 may bemounted facing upward on lower handle section 17 immediately abovecollar 69 to speed up successive measurements by placing the meter facein the operators line of sight to the cathode bar 39 which he mustobserve in placing jaws 56 over the cathode bar 39.

The jaws 56 automatically close about the current-carrying conductor bar39 by reason of the forceful application of the shoes 43 due to solelythe weight of instrument parts including jaws 56 and the yoke assembly31 against the conductor bar 39 or, if desired, by the weight of theinstrument parts together with exertion of force by the operatoractuating or causing the yoke assembly 31 including the yoke member 32to move upwardly or away from the current carrying conductor. In theclosing of jaws 56 about the conductor bar 39 a measurable electromotiveforce and hence a measurable electrical current is induced in the coilsof the jaws 56, the magnitude of which is indicative of the amount ofelectrical current passing through the conductor bar. Upon release ofthe forceful application of the shoes 43 against the conductor bar 39,the weight of the jaws 56 and yoke assembly and/or the action of thespring 73, if employed, as aforementioned cause the yoke assemblyincluding the yoke member 32 to move downwardly toward the currentcarrying conductor 39 whereby jaws 56 automatically move to their atrest, normally open position.

In another embodiment of the invention shown in FIG. 18, the currentmeasuring instrument is substantially identical to that of FIGS. 1-6 andpreviously described herein except that in this embodiment of FIG. 18the conductive coils in the normally open, conductor receptive tong-likejaws and the wiring leading to the meter unit are not utilized butinstead the tong- Iike jaws 82 are constituted of a non-retentivemagnetic material. Non-retentive magnetic jaws 82 are adapted to beoperatively associated or coupled with means for measuring theelectrical current passing through the conductor as hereafter disclosed.The non-retentive magnetic material of jaws 82 are preferablyencapsulated or covered in an electrically insulating, corrosionresistant, mechanical attach and abrasion-protecting, non-magneticsubstantially continuous layer of a material possessing such properties,for instance a synthetic resin, e.g. an epoxy resin, having suchproperties or of any other suitable material having such properties.Such layer can be a thin or thick layer and is typically of thickness inthe range of one-sixteenth inch to one-fourth inch. Depression or cavity83 is provided in the upper portion of jaw 82, depression 83 being oflarger diameter than the length of permanent magnet needle 84. Magnetneedle 84 is mounted in depression or cavity 83 and is movable on commonpivot 85 for purpose of converting magnetic flux into informationpertaining relating to the magnitude of the current flow in conductorbar 39. Cavity 83 can be in either one of jaws 82 or partly in each andlib formed by complementary curved wall portions in each jaw, i.e., witha complementary curved portion in each jaw which together form cavity33. Air gap 83a is between the inner surface of depression or cavity 83and permanent magnet needle 84. Depression or cavity $3 extends a majorportion of the distance but incompletely through the upper portion ofjaw 82 as shown. However this cavity could extend completely through theupper portion of the jaw or jaws, or a lesser or greater distance thanshown in FIG. 18 but incompletely through this jaw upper portion. Pivot85 also has indicating pointer 86 mounted thereon for moving over scale86b for indicating the magnitude of the current flow in conductor bar39. The scale 86b is previously calibrated with currents of differentamperages passing through the conductor bar encircled by the sensinghead jaws. To enable the meter man to readily see the reading on scale86b, windows can be provided in the legs of the inverted generallyU-shaped yoke member, not shown in FIG. 18 but shown in FIGS. 2, l0 andill and designated at 32 therein, by providing a larger opening in thelegs of the yoke member than provided by the weight reducing lower ormiddle aperture 42, shown in FIGS. 10 and ll, or by forming the upperand middle apertures 42 as a single large aperture but insufficientlylarge to result in excessive structural weakness. The weight reducingapertures 42, especially the lower aperture, may itself suffice forenabling the meter man to read the scale reading. instead of a directflux readout on the scale by the pointer, the readout can be indirectsuch as by use of a transducer, which translates pivot shaft rotationinto a signal for remote readout.

The terms non-retentive magnetic material and retentive magnetic usedherein mean materials characterized by low coercive force, comparativelylow hysteresis loss, relative ly high permeability, and, usually, afairly high saturation induction. Such materials are also known asmagnetically soft materials. Materials included within the meaning ofsuch terms are, for example, ingot iron, cast steel, Hypernik and castiron.

Alternatively, the sensing head jaws of the present invention canutilize one or more Hall efiect crystals in the jaws as aforementionedwith each having a core of non-retentive magnetic material andassociated transducer elements such as employed in DYN-AMP" directcurrent metering systems supplied by Halmar Electronics, inc. ofColumbus, Ohio mounted in one or more cavities or air gaps in the core.A voltmeter or other suitable meter calibrated in amperes can beutilized to indicate the value of the current through the conductorencompassed by the jaws.

For measurement of alternating current passing through the conductor,the-instrument embodiment of FIG. 18 having the non-retentive magneticsensing head jaws is utilized provided this FIG. 18 embodiment is firstmodified as follows. The permanent magnet needle, common pivot mountingthe magnet needle and the indicating pointer,.indicating pointer and thescale all shown in FIG. 18 are omitted and the depression or cavitydesignated as 83 in FIG. 18 is so dimensioned as to receive and retainby a snap fit a male member of an ammeter hereafter referred to. Suchammeter measures both alternating current and direct current by the sameammeter. The AC or DC current reading as the case may be is instantlyregistered on a scale in amperes by a pointer. Such AC and DC ammeter isreferred to as a Scale Range and is obtainable from Columbia ElectricManufacturing Company, 4ll9 Hamilton Ave., Cleveland, Ohio 4414. TheScale Ranges" referred to immediately above have a range of from 0 up to1,000 amperes, depending on the particular type Scale Range," for AC andDC current. Type AX of such Scale Range has a range of from 0 up to1,000 amperes for both AC and DC current.

In the operation of the current measuring instrument of FIGS. 1-6 tomeasure current through a conductor requiring holding of the measuringinstrument generally vertically with the jaws suspended below the handlearms or handle, the instrument is held by the meter man by handle arms23 or handle with the tong-like jaws 56 suspended vertically from andbelow the handle 15, and the weight of the instrument parts includingthe hinged jaws 56 and yoke assembly including yoke member 32 producingmoments of force acting upwardly about pivot pin 35 resulting in theopening of hinge 45 and the automatic opening of jaws 56, with thedownward movement of the yoke assembly until stopped by crossbar 27bearing against cushion washer 67 or collar 65. The extent ofdown-travel of the yoke assembly including yoke member 32 and of theopening of the hingedly mounted jaws 56 is determined by the position ofcollar 65 on yoke sleeve 30. Lowering collar 65 on yoke sleeve 30 willreduce the extent of opening of the tong-like jaws 56, whereas raisingcollar 65 on sleeve 30 will increase'the extent of opening of jaws 56.

To close the jaws 56 to substantially encompass the conductor bar 39,the entire instrument is lowered or moved by the meter man in a downwarddirection and in a fashion such that the open jaws 56 partially surroundthe conductor bar 39 and the shoes 43 contact the top of conductor bar39. The forceful application of the shoes 43 against the conductor bar39 due to weight alone of the instrument parts including jaws 56 and theyoke assembly 31 results in upward movement of the yoke sleeve 30,inverted generally U-shaped yoke member 32, and shoes 43 to producemoments of force acting downwardly about pivot pin 35 which results inthe automatic closing or clamping of jaws 56 about conductor bar 39 tosubstantially surround the bar 39. Motion stops when the end plates 88at the opposing faces of jaws 56 meet. The entire weight of theinstrument now rests on conductor bar 39. Downward force by the meterman may be exerted on the handle 15 but is not required to effectclosing of the jaws 56 around the conductor bar.

If the handle of the instrument is now released by the meter man, theinstrument will tilt slightly to the right or left to becomefree-standing by being supported on shoes 43 and on one side or sides ofcrossbars 36.

When the current measurement is completed with respect the currentthrough the conductor bar, the meter man lifts the instrument by meansof handle arms 23 or handle 15 whereby withdrawal of the forceapplication of shoes 43 against conductor bar 39 results in movementdownwardly of shoes 43, yoke sleeve 30, and inverted generally U-shapedyoke member 32. Consequently moments of force in the opposite directionare produced about pivot pin 35 whereby force is exerted upwardlythrough link arms 54 to pivot shafts 53 thereby causing the hinge membercars 51 to move upwardly, hinge 45 to open, and the tong-like jaws 56 toautomatically open. The shoes 43 remain in contact with conductor bar 39until crossbar 27 in slot 29 of the yoke sleeve 30 bears against cushionwasher 67 at which time the complete instrument with jaws 56 in fullopen, conductor receptive, position moves upwardly away from conductorbar 39 and the instrument is again in the ready-to-use state.

When in the operation of the current measuring instrument of FIGS. 1-6the ready-to-use state or position of the instrument is with the handle15 held in other than an essentially vertical position with tong-likejaws 15 suspended below such as for measurement of currents in verticalor overhead con-- ductors or conductors located laterally of the meterman, spring 73 between collar 69 and sleeve 30 is employed incompression to hold jaws 56 in the normally open conductor receptiveposition as is hereinbefore disclosed, and upon contact of the shoes 43with conductor bar or other conductor the meter man pushes the handle inthe direction of the conductor to further compress spring 73 and effect.closure of jaws 56 around the conductor. Such closing of the sensinghead jaws about the conductor is also referred to herein as automaticclosing of the jaws.

The instrument embodiment of FIG. 18 is operated to automatically closeor clamp its tong-like jaws 82 about the conductor bar for the currentmeasurement and subsequently to automatically open its jaws and removethem from the conductor bar in substantially identical manner and bysubstantially identical means as hereinbefore disclosed for theembodiment of FIGS. 1-6. Permanent magnet needle 84 is restrained in aposition substantially normal to the direction of induced magnetic fluxlines in jaw or jaws 82 generated by the current flow in conductor bar39 by means of a spring (not shown), and interraction between theinduced flux of the jaw or jaws and the flux of permanent magnet needle84 causes needle 84 to turn or rotate on its pivot an extentproportional to the flux density in the jaw or jaws and hence to theamount of current flow in conductor bar 39.

In still another embodiment of the current measuring instrument of thisinvention, with reference now to F IGS. 13, 14 and 17, nonnally open,hinged, tong-like jaws of the sensing head are designated at 91, animmovable, inverted generally U- shaped first yoke is designated at 92,and an immovable inverted generally U-shaped second yoke at 93. Thefirst and second yokes 92 and 93 respectively each include first andsecond yoke members 92a and 93a respectively of stainless steel, each ofyoke members 92a and 93a having a generally vertical lower portion, agenerally horizontal upper portion, and a curved or arcuate portionintermediate the upper and lower portions. The generally vertical lowerportion of second yoke members 93a terminates a substantial distancebelow hinge means hereafter specified. First yoke 92 is secured bywelding at its yoke members upper end portions to a lower portion of thehandle or supporting tube 140, whereas second yoke 93 is secured at itsyoke members upper end portions to the horizontal upper portion of firstyoke 92 by means of screws 94. Alternatively, second yoke 93 may haveits yoke members secured at their generally horizontal upper endportions to a lower portion of supporting tube by welding at points ofsecuring spaced from that of the first yoke members. Yoke members 92a offirst yoke 92 are secured at their lower end portions by screws to outerend portions of hinge plate halves 98. Jaws 91 of the sensing head 90are of generally arcuate, tong-like shape, are normally open forreception of the conductor, and are automatically closeable andautomatically openable when the instrument is in a generally verticalorientation with the jaws below the supporting tube 140. Each of jaws 91has conductive coils 145, shown in FIG. 14, composed of a multiplicityof windings of copper wire or other suitable electrically conductivewire wound on a non-magnetic or nonmagnetizable core of aluminum oranother non-magnetic or non-magnetizable material, and are similar orsubstantially identical to the jaws of the sensing head of theembodiment of FIGS. 1-6. Coils of jaws 91 are adapted to be operativelyconnected with electrical current measuring means hereinafter disclosed.Yoke members 93a, of the second yoke 93 have spaced apart, oppositechannels or open ended slots 99 in their lower portions, with channelsor open ended slots 99 communicating the exterior of the second yokemembers 93 with the top of slots 99,- corresponding in position witheach other, and also registering or corresponding in position withaxially aligned apertures or bores 96a through hing plate halves 98.Jaws 91 are normally open in the at rest or ready-touse, conductorreceptive state and, when closed, substantially encompass the conductor,such as cathode bar 116 in the electrolytic copper refinery tankhouse.

Hinge means 95 has pivot pin or shaft 96 inserted through registeringbores 96a through complementary hinge plate halves 98, also shown in FIG. 15. Hinge plate halves 98 mount tong-like jaws 91 by being attachedto the upper portion of jaws 91 by screws inserted through apertures 91ain hinge plate halves 98. Pivot pin 96, which is substantially centrallydisposed with reference to the hinge means, extends through registeringbores 96a in an inner end portion of each of hinge plate halves 98 witheach aperture or bore 96a being of slightly larger diameter than that ofpin 96. Pivot pins or shafts 97 extend through registering bores 97a inears 98a, shown in FIG. 15, in the movable, bifurcated or cared outerend portion of hinge plate halves 98 and in the immovable intermediatehinge portions 117, shown in FIG. 16, located between the ears 98a ofhinge plate halves 98. The first yoke members 92a of first yoke 92 aresecured at their lower portions by screws 106 to the immovable hingeportions 117. Snap rings 139 aid in retaining hinge pins 97 in place inears 98a and intermediate hinge portions 117.

Pivot pin 96 extends through the spaced apart, opposite slot apertures99 in the second yoke members 93a of second yoke 93 and is moveable inthe slots 99 as hereinafter described, pivot pin 96 also extendingthrough apertures 99a in the third yoke members 1110a of moveable,inverted generally U-shaped third yoke 100. The third yoke 1116 isunsecured to the handle or supporting tube 140 at its upper portion,with supporting tube 140 extending through an aperture or hole 141 oflarger diameter than that of the supporting tube 141 in the horizontalupper portion of third yoke 100. Third yoke 100 is disposed above andlaterally outwardly of the corresponding portions of second yoke 93.Shoes 101 of a substantially non-electrically conductive material suchas that previously disclosed herein are secured by screws to the lowerportion of each yoke member 10110 of third yoke Washers are designatedat 102 and snap rings at 103, snap rings 103 aiding in retaining thelower portions of third yoke 100 and second yoke 93 on pivot pin 96.Collar 105 of stainless steel is slideable on supporting tube 141) andis held in the desired position on supporting tube 140 between thesecond and third yokes by set screw M3. Bumper-washer 144 of a resilientmaterial, for instance, Neoprene, or any other suitable resilientmaterial, is secured to the upper portion of collar 105 by cementing,and serves as a bumper for the upper horizontal portion of third yoke100 at the end of its downward movement. Screws 109 are threadablyengaged through correspondingly internally threaded apertures in thevertical portion of yoke members 100a of third yoke 100, with screws 109projecting into slots 110 in yoke members 93a of second yoke 93 toprevent rotation of third yoke 101) about hinge pin 96. The width ofeach slot 110 is only slightly larger than the diameter of the maleportion of each screw 109. Electrically conductive wires 112 lead fromthe coil or coils 145 in the jaws 91 and pass through orifices 112a inhinge plates 98 and upwardly within the enclosed space of tubularsupporting handle or tube 140, to emerge similarly as is previouslydisclosed herein with regard the instrument of FIGS. 1-6 through anaperture or apertures in an upper tubular section of supporting tube 140to electrically connect the coils of jaw 91 with a suitable meterpackage or unit, such as the model ASARCO COP ammeter-containing packagepreviously referred to herein and obtainable from Halmar Electronics,Inc. of Columbus, Ohio. Spaced holes 113 in yoke members 100a of thirdyoke 101) are for weight reduction purpose.

Crossbars 114 also secured to a lower portion of each yoke member 1011aof third yoke 101), are of substantially identical structure and serve asubstantially identical function as the corresponding crossbars 36 ofthe instrument embodiment of FIGS. 1-6 and previously described herein.Envelopes 115 of substantially non-electrically conductive sealantmaterial, for instance silicone sealer, preferably surround otherwiseexposed portions of wires 112 for protecting and supporting wires 112.When the instrument is to be used to measure current passing through aconductor located overhead or laterally of the meter man instead ofbelow the normal level of the meter mans hands when standing with hisarms depending limply at his sides, movable collar 150 is locked at apredetermined location on the lower portion of supporting tube 140 bylocking screw 151 and helical spring 152 is disposed in a compressedstate about supporting tube 1430 between collar 150 and third yoke1111). Spring 152 bears against the horizontal portions of movable thirdyoke 100 and against the end of collar 150, and the location of collar151) locked on handle 141) is such that is provides the desired degreeof compression in spring 152 and hence the desired degree of biasing ofmovable third yoke 1111) in a direction away from the collar 150.Consequently the jaws 91 are maintained in their normally open position(except when shoes 101 are forcefully applied against the conductor) inpositions of the instrument wherein the sensing head jaws are locatedabove the handle or supporting tube or at the end portion of the handleor supporting tube when held laterally of the meter man as well as inpositions of the instrument wherein the sensing head jaws are suspendedbelow the handle or supporting tube. The remainder of the direct currentmeasuring instrument of F165. 13, 1 5 and 17 including the supportingtube or handle assembly above the yoke arms and the tong-like jaws issubstantially identical to that of the instrument embodiment of FIGS.1-6 previously disclosed herein.

In the operation of the current measuring instrument of FIGS. 13, 14 and17, with tong-like jaws 91 of sensing head in their normally open,ready-to-use, conductor-receptive position, the operator or meter manlowers the instrument by means of the supporting tube or handle 141)with only one required, to position the open jaws 91 about the cathodebar 116 in the tankhouse of an electrolytic copper refinery. After shoes101 contact cathode bar 116, and with forceful application of shoes 101against cathode bar 116 due solely to the weight of the instrument partsincluding the sensing head jaws 91 and the third yoke 100, pivot pin 96is forced upwardly in slot 99, shown in FIGS. 14 and 17, from its brokenline position, shown in FIGS. 13 and 17, to its solid line positionthereby producing moments of force acting downwardly about pivot pin 96and automatically closing jaws 91 about cathode bar 116, and involvingmovement ofjaws 91 from their broken line open position to their solidline closed position. Force may be exerted on shoes 101 by the operatorthrough the supporting tube or handle, if desired, but is not required.As jaws 91 close to substantially encompass cathode bar 116, their coils145, shownin FIG. 14, ofelectrically conductive wire cut across themagnetic line of force around cathode bar 116 and created by the directelectrical current passing through bar 1 16 thereby inducing ameasureable electromotive force and a measureable electrical current inthe coils. The operator then notes the current measurement reading onthe visible scale of the ammeter-containing package or unit, whichpreferably is mounted on the handle or supporting tube as previouslydisclosed herein with regard the embodiment of FIGS. 1-6. When theinstrument of FIGS. 13, 14 and 17 is used to measure the current passingthrough a conductor located overhead or laterally of the meter man, uponcontact of the shoes 101 with the conductor 1 16, the meter man pushesthe handle or supporting tube 140 in the direction of the conductor bar116 to further compress spring 152 and effect closure of jaws 91 aroundcathode bar 116. Such closure of jaws 91 to substantially encompass bar116 is referred to herein as automatic closing of the jaws,

' The operator then lifts the instrument from the cathode bar 116 bymeans of supporting tube 140, with only one hand required, whereby theforceful application of the shoes 101 against cathode bar 116 iswithdrawn or released and the weight of theinstrument parts includingjaws 91 and third yoke 1011 cause hinge pin 96 to move downwardly inslot 99 whereby moments of force act upwardly about pin 96 and jaws 91automatically open to their normally open, conductorreceptive position.Shoes 101 are ultimately raised out of contact with bar 116 as theinstrument is lifted higher. The operator then repeats the procedure onthe other cathode bars to measure the direct current passingtherethrough.

With reference to the current measuring apparatus of I FIGS. 19 and 20,in accordance with still another embodiment of this invention, aplurality of electrical current measuring instrument units 120 dependfrom common supporting rack or frame 126 of stainless steel. Eachcurrent measuring instrument unit comprises the common supporting rackor frame 126, a normally open, conductor-receptive, tong-like sensinghead 131 capable of utilizing the magnetic field created by theelectrical current passing through the cathode bars 122 in theelectrolytic copper refinery tankhouse for current measuring purposes,and generally vertical support arms 123 of stainless steel moveable onthe supporting rack 126 and supporting the sensing head jaws 121.Normally open, conductor receptive,

1. Apparatus for measuring electrical current passing through at leastone conductor which comprises at least one electrical current measuringinstrument, the measuring instrument comprising: a. supporting means; b.a normally open sensing head capable of utilizing a magnetic fieldcreated by the current passing through the conductor for currentmeasuring purposes, said sensing head having normally open, conductorreceptive, pivotally mounted, automatically closeable and automaticallyopenable jaws at least when the instrument is in a generally verticalorientation with the jaws below the supporting means, the jaws whenclosed substantially encompassing the conductor for the currentmeasuring; c. means moveable on the supporting means of (a) andsupporting the normally open sensing head jaws; d. means pivotallymounting the jaws on the last-mentioned moveable supporting means; e.means connecting outer end portions of the pivoted jaw mounting meanswith the supporting means; f. means maintaining the jaws in an openposition when contacting means hereafter specified is not forcefullyapplied against a solid surface; and g. contacting means attached to thelast-mentioned moveable supporting means, forceful application of thecontacting means against a solid surface effecting movement of themoveable supporting means in a direction resulting in the closing of thejaws to substantially encompass the conductor and withdrawal of theforceful application of the contacting means from against the solidsurface resulting in movement of the moveable supporting means in adifferent direction to effect the opening of the jaws at least when theinstrument is in a generally vertical orientation with the jaws belowthe supporting means; h. the sensing head adapted to be operativelyassociated with means for measuring the electrical current passingthrough the conductor.
 2. An instrument for measuring electrical currentpassing through a conductor, which comprises: a. supporting means; b. anormally open sensing head capable of utilizing a magnetic field createdby the current passing through the conductor for current measuringpurposes, said sensing head having normally open, conductor receptive,pivotally mounted, automatically closeable and automatically openablejaws at least when the instrument is in a generally vertical orientationwith the jaws below the supporting means, the jaws when closedsubstantially encompassing the conductor for the current measuring; c.means moveable on the supporting means of (a) and supporting thenormally open sensing head jaws; d. means pivotally mounting the jaws onthe last-mentioned moveable supporting means; e. means connecting outerend portions of the pivoted jaw mounting means with the supportingmeans; f. means maintaining the jaws in an open position when contactingmeans hereafter specified is not forcefully applied against a solidsurface; and g. contacting means attached to the last-mentioned moveablesupporting means, forceful application of the contacting means against asolid surface effecting movement of the moveable supporting means in adirection to result in the automatic closing of the jaws tosubstantially encompass the conductor and withdrawal of forcefulapplication of the contacting means from against the solid surfaceresulting in movement of the moveable supporting means in a differentdirection to effect the automatic opening of the jaws when theinstrument is in a generally vertical orientation with the jaws belowthe supporting means; h. the sensing head adapted to be operativelyassociated with means for measuring the electrical current passingthrough the conductor.
 3. An instrument for measuring direct electricalcurrent passing through a conductor, which comprises: a. supportingmeans; b. a normaLly open sensing head capable of utilizing a magneticfield created by the current passing through the conductor for currentmeasuring purposes, said sensing head having normally open, conductorreceptive, hinged, automatically closeable and automatically openablejaws when the instrument is in a generally vertical position with thejaws below the supporting means, the jaws when closed substantiallyencompassing the conductor for the current measuring; c. moveable yokemeans including an inverted generally U-shaped yoke member moveable onthe supporting means and supporting the normally open sensing head jaws;d. hinge means including a substantially centrally disposed, withreference to a upper portion of the hinge means, pivot pin hingedlymounting the jaws on the movable yoke means yoke member; e. link meanspivotally interconnecting and linking outer end portions of the hingemeans with a lower portion of the supporting means; f. means maintainingthe jaws in an open position when contacting means hereafter specifiedis not forcefully applied against the conductor; and g. contacting meansof a substantially non-electrically conductive material attached to alower portion of the yoke means yoke member and extending beyond theyoke member end, forceful application of the contacting means againstthe conductor effecting movement of the yoke member in a direction toresult in closing of the jaws to substantially encompass the conductor,and withdrawal of forceful application of the contacting means fromagainst the conductor resulting in movement of the moveable yoke memberin an opposite direction when the instrument is in a generally verticalorientation with the jaws below the supporting means, to effect openingof the jaws; h. the sensing head adapted to be operatively associatedwith means for measuring the electrical current passing through theconductor.
 4. An instrument for measuring direct electrical currentpassing through a bar conductor, which comprises: a. an elongate handle;b. a normally open tong-like sensing head capable of utilizing amagnetic field created by the current passing through the conductor forcurrent measuring purposes, said sensing head having normally open,conductor receptive, hinged, tong-like, automatically closeable andautomatically openable jaws when the instrument is in a generallyvertical orientation with the jaws below the handle, the jaws whenclosed substantially encompassing the conductor for the currentmeasuring; c. a moveable yoke assembly including an inverted generallyU-shaped yoke member moveable on the handle and supporting the normallyopen sensing head jaws; d. hinge means hingedly mounting the jaws on theinverted generally U-shaped yoke member, said hinge means includinghinge plates secured to upper portions of the jaws by a substantiallycentrally disposed, with reference to the hinge means, pivot pinextending through the passageways of axially aligned sleeves eachaffixed to an inner end portion of a different hinge plate and throughregistering orifices in the inverted generally U-shaped yoke member; e.link means pivotally interconnecting and linking outer end portions ofthe hinge means hinge plates with a lower portion of the handle; f. theweight of instrument parts including the sensing head jaws and themoveable yoke assembly maintaining the jaws in an open position whenshoes hereafter specified are not forcefully applied against theconductor; g. means limiting the extent of opening of the jaws butallowing them to open sufficiently wide to enable said jaws to bepositioned about the conductor; and h. shoes of a substantiallynon-electrically conductive material attached to a lower portion of theinverted generally U-shaped yoke member and extending beyond the yokemember end, forceful application of the shoes against the conductoreffecting movement of the moveable yoke assembly in a direction toproduce moments of force aBout the centrally disposed pivot pin therebyresulting in closing of the jaws to substantially encompass theconductor and withdrawal of the forceful application of the shoes fromagainst the conductor resulting in movement of the moveable yokeassembly in an opposite direction thereby resulting in opening of thejaws when the instrument is in a generally vertical orientation with thejaws below the handle; i. the sensing head adapted to be operativelyas-sociated with means for measuring the electrical current passingthrough the conductor.
 5. An instrument for measuring direct electricalcurrent passing throug a bar conductor, which comprises: a. an elongatehandle; b. a normally open, tong-like sensing head capable of utilizinga magnetic field created by the current passing through the conductorfor current measuring purposes, said sensing head having normally open,conductor receptive, hinged, tong-like, automatically closeable andautomatically openable jaws when the instrument is in a generallyvertical orientation with the jaws below the handle, the jaws havinggenerally arcuate inner surfaces, said jaws when closed substantiallyencompassing the conductor for the current measuring; c. moveable yokemeans including an inverted generally U-shaped yoke member moveable onthe handle and supporting the normally open tong-like jaws; d. hingemeans hingedly mounting the jaws on the moveable yoke means yoke member,said hinge means including hinge plates secured to upper portions of thejaws, and a substantially centrally disposed, with reference to thehinge means, pivot pin extending through axially aligned sleeves eachaffixed to an inner end portion of a different hinge plate and throughregistering orifices in the inverted generally U-shaped yoke member; e.links pivotally connected to and linking outer end portions of the hingemeans hinge plates with outer end portions of a crossbar affixed in aslot in a lower portion of the handle; f. the crossbar affixed in theslot in the lower portion of the handle; g. the weight of instrumentparts including the sensing head jaws and the moveable yoke meansmaintaining the tong-like jaws in an open position when shoeshereinafter specified are not forcefully applied against the conductor;h. means limiting the extent of opening of the jaws but allowing them toopen sufficiently wide to enable said jaws to be positioned about theconductor; and i. shoes of a substantially non-electrically conductivematerial attached to a lower portion of the inverted generally U-shapedyoke member and extending beyond the yoke member end, forcefulapplication of the shoes against the conductor effecting movement of theyoke member in a direction to produce moments of force about thecentrally disposed hinge pin thereby resulting in closing of the jaws tosubstantially encompass the conductor, and withdrawal of forcefulapplication of the shoes from against the conductor resulting inmovement of the yoke member in an opposite direction due to the weightof instrument parts including the sensing head jaws and moveable yokeassembly thereby resulting in opening of the jaws when the instrument isin a generally vertical orientation with the jaws below the handle; j.the sensing head adapted to be operatively associated with means formeasuring the direct current passing through the conductor.
 6. Aninstrument for measuring direct electrical current passing through a barconductor which comprises: a. an elongate handle; b. a normally opentong-like sensing head capable of utilizing a magnetic field created bythe current passing through the conductor bar for current measuringpurposes, said sensing head having normally open, conductor receptive,hinged, generally arcuate, tong-like, automatically closeable andautomatically openable jaws when the instrument is in a generallyvertical orientation with the jaws below the handle, the jaws whenclosed substantially encoMpassing the conductor for the currentmeasuring; c. a moveable yoke assembly including an inverted generallyU-shaped yoke member moveable on the handle and supporting the normallyopen tong-like jaws; d. hinge means hingedly mounting the jaws on theinverted generally U-shaped yoke member, said hinge means including twohinge plates secured to upper portions of the jaws and a substantiallycentrally disposed, with reference to the hinge means, pivot pinextending through the passageway of two axially aligned sleeves eachaffixed to an inner end portion of a different hinge plate and throughregistering orifices in the inverted generally U-shaped yoke member; e.links pivotally interconnecting and linking outer end portions of thehinge means hinge plates with outer end portions of a crossbar affixedin a slot in the lower portion of the handle; f. the crossbar affixed inthe slot in the lower portion of the handle; g. the weight of instrumentparts including the sensing head jaws and moveable yoke assemblymaintaining the jaws in an open position when the shoes hereinafterspecified are not forcefully applied against the conductor; h. meanslimiting the extent of opening of the jaws but allowing them to opensufficiently wide to enable said jaws to be positioned about theconductor; and i. shoes of a substantially non-electrically conductivematerial attached to a lower portion of and extending beyond the end ofthe inverted generally U-shaped yoke member, forceful application of theshoes against the conductor effecting movement of the moveable yokeassembly in a direction to produce moments of force about the centrallydisposed pivot pin thereby resulting in closing of the jaws tosubstantially encompass the conductor, and withdrawal of the forcefulapplication of the shoes from against the conductor resulting inmovement of the moveably yoke assembly in an opposite direction due tothe weight of instrument parts including the sensing head jaws andmoveable yoke assembly thereby resulting in opening of the jaws when theinstrument is in a vertical orientation with the jaws below the handle;j. the sensing head adapted to be operatively associated with means formeasuring the direct electrical current passing through the conductor.7. An instrument for measuring direct electrical current passing througha bar conductor which comprises: a. an elongate handle; b. a normallyopen, tong-like sensing head capable of utilizing a magnetic fieldcreated by the current passing through the conductor bar for currentmeasuring purposes, said sensing head having normally open, conductorreceptive, hinged, generally arcuate, tong-like, automatically closeableand automatically openable jaws when the instrument is in a generallyvertical orientation with the jaws below the handle which, when closed,substantially encompass the bar conductor for the current measuring; c.a moveable yoke assembly including a yoke sleeve moveable on the handlelower portion, a narrow width slot in a lower portion of said yokesleeve, the slot being of larger width than that of the thickness of acrossbar affixed in a slot in the lower portion of a lower section ofthe handle, and an inverted generally U-shaped yoke member secured to anupper portion of the yoke sleeve, said yoke member being moveable on thehandle together with said yoke sleeve; d. the crossbar affixed in theslot in the handle lower portion and disposed in the yoke sleeve slot;e. hinge means hingedly mounting the jaws on the inverted generallyU-shaped yoke member, the hinge means including hinge plates secured toupper portions of the jaws and a substantially centrally disposed, withreference to the hinge means, pivot pin extending through thepassageways of axially aligned sleeves each affixed to an inner endportion of a different hinge plate and through registering orifices inthe inverted generally U-shaped yoke member; f. links pivotallyInterconnecting and linking outer end portions of the hinge means hingeplates with outer end portions of the crossbar of (d); g. the weight ofinstrument parts including the sensing head jaws and moveably yokeassembly maintaining the jaws in an open position when the shoeshereafter specified are not forcefully applied against the conductor; h.means limiting the extent of opening of the jaws but allowing them toopen sufficiently to enable said jaws to be positioned about theconductor; and i. shoes of a substantially non-electrically conductivematerial attached to a lower portion of and extending beyond the end ofthe inverted generally U-shaped yoke member, forceful application of theshoes against the conductor bar due to the weight of instrument partsincluding the sensing head jaws and moveable yoke assembly effectingmovement of the moveable yoke assembly in a direction to produce momentsof force about the centrally disposed pivot pin thereby resulting inclosing of the jaws to substantially encompass the conductor bar andwithdrawal of the forceful application of the shoes from against theconductor bar resulting in movement of the moveable yoke assembly in anopposite direction due to the weight of instrument parts including thesensing head jaws and the moveable yoke assembly thereby resulting inopening of the jaws when the instrument is in a generally verticalorientation with the jaws below the handle; j. the sensing head adaptedto be operatively associated with means for measuring the directelectrical current passing through the bar conductor.
 8. The instrumentof claim 7 wherein the sensing head normally open, conductor receptivetong-like jaws each comprise a non-magnetic core, and at least oneelectrically conductive wire coil on each core, the coils each having amultiplicity of windings and being electrically connected in series andadapted to be operatively electrically connected to the direct currentmeasuring means.
 9. The instrument of claim 8 wherein the wire of eachcoil is coated with a thin layer of an electrically insulating material.10. The instrument of claim 9 wherein each tong-like jaw has anelectrically insulating, corrosion resistant, mechanical attack-andabrasion-protecting non-magnetic layer of a material possessing suchproperties in said layer over the coil windings of each jaw.
 11. Theinstrument of claim 10 wherein the bar conductor is a cathode bar in anelectrolytic copper refinery tankhouse, and the tong-like jaws are sodimensioned as to readily pass between the cathode bar and immediatelyadjacent cathode bars to enable closing of the jaws about thefirst-mentioned cathode bar with the plane of said jaws beingsubstantially normal to a major axis of the first-mentioned cathode bar.12. The instrument of claim 11 wherein the material of the electricallyinsulating, corrosion resistant, mechanical attack-andabrasion-protecting, non-magnetic layer is a synthetic resin having suchproperties in said layer.
 13. The instrument of claim 12 wherein thesynthetic resin is an epoxy resin.
 14. The instrument of claim 10further characterized by having means effecting the automatic opening ofthe sensing head jaws and maintaining of said jaws in an open positionwhen the shoes are not forcefully applied against the conductor when theinstrument is in a generally vertical orientation with the jaws abovethe supporting means or in a generally horizontal orientation with thejaws lateral of the supporting means, as well as in a generally verticalorientation with the jaws below the supporting means.
 15. The instrumentof claim 14 wherein the automatic jaws opening effecting and jaws openposition maintaining means is a helical spring disposed about a lowerportion of the handle between and bearing against a shiftable collarlocked on the handle lower portion and against the moveable yoke sleeve,the collar being locked at a desired position on the handle lowerportion to provide a desired Degree of compression in the helical springand a consequent desired degree of biasing of the moveable yoke sleevesufficient to effect the automatic opening of the jaws and themaintaining of the jaws in the open position when the shoes are notforcefully applied against the conductor.
 16. The instrument of claim 11wherein generally horizontal and substantially parallel crossbars areattached to a lower portion of the legs of the inverted generallyU-shaped yoke member, the crossbars each extending an appreciabledistance laterally beyond the side edges of each leg, a lowermost edgeof each crossbar when the instrument is in a generally verticalorientation with the jaws below the handle being above a lower edge ofeach shoe.
 17. The instrument of claim 10 wherein the means limiting theopening extent of the jaws is a shiftable collar locked in a desiredlocation on the yoke sleeve, and a cushion washer of resilient materialis disposed between the shiftable collar locked on the yoke sleeve andthe crossbar affixed in the slot in the handle lower portion anddisposed in the yoke sleeve slot.
 18. The instrument of claim 11 whereinthe sensing head coils are operatively electrically connected to thedirect current measuring means, said current measuring means comprisingan ammeter-containing meter unit also containing circuit means.
 19. Theinstrument of claim 18 wherein the ammeter-containing meter unit ismounted on the instrument handle.
 20. The instrument of claim 19 whereinthe ammeter-containing meter unit is mounted on a top portion of theinstrument handle.
 21. The instrument of claim 20 wherein the meter unithas a short length of tube of larger diameter than that of a top portionof the instrument handle secured to a back side plate of a casing of themeter unit, the meter unit being removably mounted on a top portion ofthe instrument handle by means of said tube being disposed over the topportion of the handle.
 22. The instrument of claim 7 whereinattrition-preventing plates are secured to confronting end faces of thetong-like jaws.
 23. An instrument for measuring direct current passingthrough a bar conductor which comprises: a. an elongate supporting tubeincluding an upper tubular section, a lower tubular section, andflexible joint means uniting the lower portion of the upper section withthe upper portion of the lower section; b. a normally open, tong-likesensing head capable of utilizing a magnetic field created by thecurrent passing through the conductor bar for current measuringpurposes, said sensing head having normally open, hinged, tong-likeautomatically closeable and automatically openable jaws when theinstrument is in a generally vertical orientation with the jaws belowthe handle which, when closed, substantially encompass the conductor forthe current measuring; c. a moveable yoke assembly including a yokesleeve moveable on the supporting tube lower section, a narrow widthslot in a lower portion of said sleeve, the slot being of larger widththan the thickness of a crossbar affixed in a slot in the lower portionof the supporting tube lower section and disposed in the yoke sleeveslot, and an inverted generally U-shaped yoke member secured to an upperportion of the yoke sleeve, said yoke member being moveable on thesupporting tube lower section with the yoke sleeve; d. the crossbaraffixed in the slot in the supporting tube lower tubular section anddisposed in the yoke sleeve slot, said crossbar having an aperture ineach opposite end portion; e. hinge means including a substantiallycentrally disposed, with reference to the hinge means, pivot pinextending through passageways of two axially aligned sleeves eachaffixed to an inner end portion of a different hinge plate and throughregistering orifices in the inverted generally U-shaped yoke member, andthe hinge plates secured to upper portions of the tong-like jaws, eachhinge plate having two spaced apart, axially aligned annulaR memberssecured to a generally downwardly extending outer end portion of saidhinge plate; f. fastening members securing the hinge plates to the upperportions of the tong-like jaws; g. a shiftable collar slideable on theyoke sleeve, and means locking the collar at a predetermined location onthe sleeve, said collar limiting the extent of opening of the tong-likejaws by abutting against the crossbar after a predetermined distance ofdownward movement of the yoke sleeve and the inverted generally U-shapedyoke member secured thereto; h. link arms each having a longitudinallyslotted end portion with transverse axially aligned apertures throughthe slotted end portion and an aperture in the opposite end portionthereof, each link arm pivotally connected to the crossbar by receivingan apertured end portion of the crossbar in its slotted end portion insuch manner that the crossbar apertures and link arm slotted end portionapertures register, and pivot pins through the registering apertures ofthe crossbars and of the slotted and apertured linkage arm end portions,and each link arm also pivotally connected at its opposite apertured endportion to each hinge plate outer end portion by a pivot pin throughregistering apertures of the hinge plate axially aligned annular membersand of said opposite apertured end portion of the link arm, saidopposite apertured end portion of the link arm being positioned betweenthe spaced axially aligned annular members of the hinge plate outer endportion; i. the weight of instrument parts including the sensing headjaws and moveable yoke assembly maintaining the jaws in an open positionwhen the shoes hereafter specified are not forcefully applied againstthe conductor; and j. shoes of substantially non-electrically conductivematerial attached to a lower end portion of the inverted generallyU-shaped yoke member legs and extending beyond the lower ends of saidyoke member legs, the shoes contacting the bar conductor upon downwardlowering movement of the instrument whereby due to the weight ofinstrument parts including the sensing head jaws and moveable yokeassembly, the shoes, inverted generally U-shaped yoke member and yokesleeve move upwardly to produce moments of force about the centrallydisposed pivot pin thereby resulting in movement of the jaws to a closedposition substantially encompassing the bar conductor and withdrawal offorceful application of the shoes from the bar conductor by an upwardlifting movement of the instrument resulting in movement downwardly ofthe shoes, yoke sleeve and the inverted generally U-shaped yoke memberdue to the weight of instrument parts including the sensing head jawsand moveably yoke assembly thereby resulting in movement of the jaws totheir normally open, conductor receptive position when the instrument isin a generally vertical orientation with the jaws below the supportingtube; k. the sensing head adapted to be electrically connected to anammeter-containing unit also containing circuit means for measuring thecurrent passing through the conductor.
 24. An instrument for measuringelectrical current passing through a conductor, which comprises: a.supporting means; b. a normally open, sensing head capable of utilizinga magnetic field created by the current through the conductor forcurrent measuring purposes, said sensing head having normally open,pivotally mounted, automatically closeable and automatically openablejaws when the instrument is in a generally vertical orientation with thejaws below the supporting means of a non-retentive magnetic material,the jaws when closed substantially encompassing the conductor for thecurrent measuring; c. means moveable on the supporting means of (a) andsupporting the normally open sensing head jaws; d. means pivotallymounting the jaws on the last-mentioned moveable supporting means; e.means connecting outer end portions of the pivotal jaw mounting meanswith the supporting means; f. means maintaining the jaws in an openposition when a contacting means hereinafter specified is not forcefullyapplied against the solid surface; and g. contacting means attached tothe moveable yoke assembly, forceful application of the contacting meansagainst a solid surface effecting movement of the moveable supportingmeans in a direction to result in the automatic closing of the jaws tosubstantially encompass the conductor and withdrawal of the forcefulcontacting means application from against the solid surface resulting inmovement of the moveable supporting means in a different direction whenthe instrument is in a generally vertical orientation with the jawsbelow the supporting means to effect the automatic opening of the jaws;h. the sensing head adapted to be operatively associated with means formeasuring the electrical current passing through the conductor.
 25. Theinstrument of claim 24 wherein the sensing head is operativelyassociated with the current measuring means and said current measuringmeans comprises a permanent magnet needle rotatably mounted on a pivotdisposed in a cavity formed in at least one of the non-retentivemagnetic jaws, said magnet needle being restrained in a positionsubstantially normal to induced flux lines in the jaw, interactionbetween the induced flux of the jaw and the permanent magnet needle fluxcausing the magnet needle to turn on its pivot an extent proportional tothe amount of electrical current through the bar conductor.
 26. Aninstrument for measuring direct electrical current passing through a barconductor which comprises: a. supporting means; b. a normally opentong-like sensing head capable of utilizing a magnetic field created bythe current through the conductor for current measuring purposes, saidsensing head having normally open, hinged, tong-like, automaticallycloseable and automatically openable jaws when the instrument is in agenerally vertical orientation with the jaws below the supporting means,of a non-retentive magnetic material, the jaws when closed substantiallyencompassing the conductor for the current measuring; c. moveable yokemeans including an inverted generally U-shaped yoke member moveable onthe supporting means and supporting the normally open sensing head jaws;d. hinge means including a substantially centrally disposed, withreference to the hinge means, pivot pin hingedly mounting the jaws onthe moveable yoke means yoke member; e. links pivotally interconnectingand linking outer end portions of the hinge means with a lower portionof the supporting means; f. means maintaining the jaws in an openposition when shoes hereafter specified are not forcefully appliedagainst the solid surface; g. means limiting the extent of opening ofthe jaws but allowing them to open sufficiently wide to enable the jawsto be positioned about the conductor; and h. shoes of a substantiallynon-electrically conductive material attached to a lower portion of theyoke means yoke member and extending beyond the yoke member end,forceful application of the shoes against a solid surface effectingmovement of the yoke member in a direction to produce moments of forceabout the centrally disposed hinge pin thereby resulting in closing ofthe jaws to substantially encompass the conductor bar and withdrawal offorceful application of the shoes from against the solid surfaceresulting in movement of the yoke member in an opposite direction due tothe weight of instrument parts including the sensing head jaws andmoveable yoke assembly thereby resulting in opening of the jaws when theinstrument is in a generally vertical position with the jaws below thesupporting means; i. the sensing jaws adapted to be operativelyassociated with magnetic flux-utilizing current measuring means formeasuring the electrical current passing through the conductor.
 27. Theinstrument of claim 26 wherein the sensing head is operativelyassOciated with the current measuring means and said current measuringmeans comprises a permanent magnet needle rotatably mounted on a pivotdisposed in a cavity form ed in at least one of the non-retentivemagnetic jaws, said magnet needle being restrained in a positionsubstantially normal to induced flux lines in the jaw, interactionbetween the induced flux of the jaw and the permanent magnet needle fluxcausing the magnet needle to turn on its pivot an extent proportional tothe amount of electrical current through the bar conductor.
 28. Aninstrument for measuring direct electrical current passing through a barconductor which comprises: a. an elongate handle; b. a normally opentong-like sensing head capable of utilizing a magnetic field created bythe current through the conductor for current measuring purposes, saidsensing head having normally open, hinged, tong-like automaticallycloseable and automatically openable jaws when the instrument is in agenerally vertical orientation with the jaws below the supporting means,of a non-retentive magnetic material, the jaws when closed substantiallyencompassing the conductor for the current measuring; c. moveable yokemeans including an inverted generally U-shaped yoke member moveable onthe elongate handle and supporting the normally open sensing head jaws;d. hinge means hingedly mounting the jaws on the moveable yoke meansyoke member, said hinge means including hinge plates secured to upperportions of the jaws, and a substantially centrally disposed, withreference to the hinge means, pivot pin extending through at least onesleeve affixed to inner end portions of the hinge plates and throughregistering orifices in the inverted generally U-shaped yoke member; e.links pivotally interconnecting and linking outer end portions of thehinge means hinge plates with outer end portions of a crossbar affixedin a slot in a lower portion of the handle; f. the crossbar affixed inthe slot in the handle lower portion; g. the weight of instrument partsincluding the sensing head jaws and the moveable yoke means maintainingthe tong-like jaws in an open position when shoes hereinafter specifiedar not forcefully applied against the conductor; h. means limiting theextent of opening of the jaws but allowing them to be openedsufficiently wide to enable the jaws to be positioned about theconductor; and i. shoes of a substantially non-electrically conductivematerial attached to a lower portion of the inverted generally U-shapedyoke member and extending beyond the yoke member end, forcefulapplication of the shoes against the conductor due to the weight ofinstrument parts including the sensing head jaws and moveable yoke meanseffecting movement of the yoke member in a direction to produce momentsof force about the pivot pin thereby resulting in closing of the jawsabout the conductor and withdrawal of forceful application of the shoesfrom the conductor resulting in movement of the yoke member in anopposite direction due to the weight of instrument parts including thesensing head jaws and moveable yoke assembly thereby resulting inopening of the jaws when the instrument is in a generally verticalorientation with the jaws below the handle; j. the sensing head adaptedto be operatively associated with means for measuring the direct currentpassing through the conductor.
 29. The instrument of claim 28 whereinthe sensing head is operatively associated with the current measuringmeans and said current measuring means comprises a permanent magnetneedle rotatably mounted on a pivot disposed in a cavity formed in atleast one of the non-retentive magnetic jaws, said magnet needle beingrestrained in a position substantially normal to induced flux lines inthe jaw, interaction between the induced flux of the jaw and thepermanent magnet needle flux causing the magnet needle to turn on itspivot an extent proportional to the amount of electrical current througHthe bar conductor.
 30. An instrument for measuring electrical currentpassing through a conductor, which comprises: a. supporting means; b. anormally open sensing head capable of utilizing a magnetic field createdby the current passing through the conductor for current measuringpurposes, said sensing head having hinged, normally open, conductorreceptive automatically closeable and automatically openable jaws whenthe instrument is in a generally vertical orientation with the jawsbelow the supporting means, the jaws when closed substantiallyencompassing the conductor for the current measuring; c. an immovableinverted generally U-shaped first yoke including first yoke memberssecured at their generally horizontal upper end portions to a lowerportion of the supporting means, and at their generally vertical lowerend portions to outer end portions of hinge means mounting the jaws; d.an immovable inverted generally U-shaped second yoke including secondyoke members secured at their generally horizontal upper end portions tothe generally horizontal upper end portions of the first yoke members orto a lower portion of the supporting means at points of securing spacedfrom that of the first yoke members, said second yoke members havinggenerally vertical intermediate portions and generally vertical lowerend portions below the hinge means, said second yoke members havingspaced, opposite, open-ended slots in a lower portion thereof, thesecond yoke members open-ended slots registering with an aperturethrough the hinge means; e. the hinge means mounting the sensing headjaws, said hinge means having the aperture extending therethrough; f. asubstantially centrally disposed, with reference to the hinge means,pivot pin disposed in the aperture through the hinge means, the pivotpin also extending through and moveable in the slot of said second yokemembers and through spaced, opposite, orifices in lower generallyvertical portions of third yoke members of a moveable third yoke; g. amoveable inverted generally U-shaped third yoke including the third yokemembers having the spaced, opposite orifices in the lower generallyvertical portions thereof, said third yoke being unsecured at itsgenerally horizontal upper end portion and the generally vertical lowerportion of said third yoke being spaced laterally outwardly of thesecond yoke and substantially parallel to the second yoke generallyvertical intermediate and lower end portions; h. means securing saidthird yoke and hence said second yoke on the pivot pin; i. meansmaintaining the jaws in an open position when shoes hereafter specifiedare not applied against the conductor; and j. shoes attached to a lowerportion of said third yoke members and extending beyond lower endsthereof, forceful application of the shoes against the conductorresulting in closing of the jaws to substantially encompass theconductor and withdrawal of forceful application of the shoes fromagainst the conductor resulting in opening of the jaws when theinstrument is in a generally vertical orientation with the jaws belowthe supporting means; k. the sensing head adapted to be operativelyassociated with means for measuring the current passing through theconductor.
 31. The instrument of claim 30 wherein the sensing headnormally open, tong-like jaws each include a non-magnetic core, and atleast one conductive wire coil on each core, the coils each including amultiplicity of windings and connected in series and to a currentmeasuring means.
 32. The instrument of claim 31 wherein the wire of eachcoil is coated with a layer of electrically insulating material.
 33. Theinstrument of claim 32 wherein each jaw has an electrically insulating,corrosion resistant, mechanical attack and abrasion-protectingnon-magnetic layer of a material possessing such properties in saidlayer over the coil windings of each jaw.
 34. The instrument of claim 33wherein the materiAl of the electrically insulating, corrosionresistant, mechanical attack and abrasion-protecting, non-magnetic layeris a synthetic resin having such properties in said layer.
 35. Aninstrument for measuring direct electrical current passing through aconductor, which comprises: a. an elongate handle; b. a normally opensensing head capable of utilizing a magnetic field created by thecurrent passing through the conductor for current measuring purposes,said sensing head having hinged, normally open, automatically closeableand automatically openable, jaws when the instrument is in a generallyvertical orientation with the jaws below the handle, the jaws whenclosed substantially encompassing the conductor for the currentmeasuring; c. an immovable inverted generally U-shaped first yokeincluding first yoke members secured at their generally horizontal upperend portions to a lower portion of the supporting means, and at theirgenerally vertical lower end portions to outer end portions of hingemeans mounting the jaws; d. an immovable inverted generally U-shapedsecond yoke including second yoke members secured at their generallyhorizontal upper end portions to the generally horizontal upper endportions of the first yoke members or to a lower portion of thesupporting means at points of securing spaced from that of the firstyoke members, said second yoke members having generally verticalintermediate portions and generally vertical lower end portions belowthe hinge means, said second yoke members having spaced, opposite,open-ended slots in a lower portion thereof, the second yoke membersopen-ended slots registering with registering apertures through thehinge means hinge plates hereafter specified; e. the hinge meansmounting the sensing head jaws, said hinge means comprising the hingeplates secured to an upper portion of the jaws and having theregistering apertures extending therethrough; f. a substantiallycentrally disposed, with reference to the hinge means, pivot pindisposed in the apertures through the hinge plates, the pivot pin alsoextending through and moveable in the slot of said second yoke membersand through spaced, opposite, orifices in lower generally verticalportions of third yoke members of a moveable third yoke; g. a moveableinverted generally U-shaped third yoke including the third yoke membershaving the spaced opposite orifices in the lower generally verticalportions thereof, said third yoke being unsecured at its generallyhorizontal upper end portion and the generally vertical lower portion ofsaid third yoke being spaced laterally outwardly of the second yoke andsubstantially parallel to the second yoke generally verticalintermediate and lower end portions; h. means securing said third yokeand hence said second yoke on the pivot pin; i. the weight of instrumentparts including the sensing head jaws and the third yoke maintaining thejaws in an open position when shoes hereafter specified are notforcefully applied against the conductor; j. shoes of a substantiallynon-electrically conductive material attached to a lower portion of saidthird yoke members and extending beyond lower ends thereof, forcefulapplication of the shoes against the conductor resulting in upwardmovement of the substantially centrally disposed pivot pin in the secondyoke slot aperture thereby resulting in the automatic closing of thejaws to substantially encompass the conductor and withdrawal of theforceful application of the shoes from against the conductor resultingin downward movement of the pivot pin in the second yoke slots therebyresulting in the automatic opening of the jaws when the instrument is ina generally vertical orientation with the jaws below the handle; and k.means operatively associated with the sensing head for measuring thecurrent passing through the conductor.